Last week's three-day surge of sick calls by Muni operators left many transit riders waiting, sometimes as long as an hour, for their buses, trains and streetcars to arrive. If they felt like pawns in contentious labor negotiations, that's because they were.

Anyone hoping for a quick resolution of the labor dispute through a scheduled Saturday arbitration hearing will have to keep waiting. Representatives of the Municipal Transportation Agency and Transport Workers Local 250-A met with a mediator Friday but called off a Saturday arbitration session set by the City Charter.

"The union declined to meet in arbitration" Saturday, said Paul Rose, an MTA spokesman. "We are working with them to sit down and talk in mediation to finalize this agreement and provide our operators with a good and fair contract."

Should the union fail to approve a mediated agreement or participate in arbitration by the June 15 deadline, Rose said, the current contract would remain in effect for the next two years - and operators would go without raises.

Just as BART commuters were caught - twice - in the middle of a dispute between workers and management last year, last week the folks who take 715,000 trips on Muni each weekday got their turn, even though San Francisco city workers are prohibited from work stoppages.

The mass absence came after operators, represented by Transport Workers Union Local 250-A, rejected a proposed agreement, reached with the aid of a mediator, on May 30. It called for an 11.25 percent raise over two years - raising the base pay to $32 an hour on July 1 - but required workers to make a 7.5 percent pension contribution now paid by the city.

Union officials have said the pension payments will erode the raises, the first in years. Operators complain that the offer is unreasonable and continues an atmosphere of blaming them for the agency's financial struggles, poor on-time performance and unreliability.

Operators say that's what led to last week's sickout, a protest they and the union say was orchestrated on the grassroots level - out of anger - to send a message to MTA management.

"This is a concerted attack on SFMTA and definitely not on our passengers," said an operator and union activist who did not want his name used for fear of retribution.

Whether or not they're the intended target, commuters suffer when a transit agency shuts down. BART's strikes and protracted contract dispute last year produced an outburst of commuter anger - and cries for a ban on transit strikes.

That cry faded, but didn't disappear, once trains started running. Proposed legislation to ban transit strikes failed to gain any traction in Sacramento. And last week, Steve Glazer, an Assembly candidate who ran on a platform to ban BART strikes, failed to get enough votes to advance to November's general election.

The Muni sickout also shows that a strike ban is no magic bullet.

"By itself, prohibiting strikes does not lead to cooperative labor-management relations," said John Logan, director of the Labor and Employment Studies program at San Francisco State University.

All city employees are prohibited from striking, but Proposition G, approved by voters in 2010, added to the City Charter new rules pertaining to Muni alone. The ballot measure removed a provision requiring Muni operators be paid the second-highest wage in the nation. It also altered the arbitration process, which occurs when a contract proposal is rejected by members, so the arbitrator cannot rule against the MTA's proposals unless the union can prove that its interests outweigh "the public interest in efficient and reliable transit."

The union contends that is an unreasonably high standard. Before the contract vote, in which leaders made no recommendations, local President Eric Williams called the impasse resolution process "lopsided and unfair" and urged the membership to take a stand. Members voted down the proposal 1,198-47. Three days later, hundreds of operators were calling in sick.

"Unions turn to things like sickouts when the law takes away other options," said Gordon Lafer, an associate professor of labor studies at the University of Oregon. "The traditional framework for public sector bargaining was to have binding arbitration that's neutral. If it becomes something that employees see as tilted, no longer equal, it pushes them to be creative."

The choice of a sickout, while unusual in San Francisco, is not uncommon among workers banned from striking - police officers, teachers (in some states, but not California), airline pilots, air traffic controllers - labor experts said.

"This is a long history of public workers using sickouts as a negotiating tool when they lack other leverage," said Joseph McCartin, a Georgetown University history professor and author of a book about the 1981 air traffic controllers strike.

"When police unions staged sickouts they were referred to as the 'blue flu.' When firefighters used them they were called the 'red rash,' and teachers spoke of getting 'chalk dust fever,' " he said.

While sickouts and strikes can have the same effect - long waits, costly cab rides or lengthy walks - one advantage of a strike is that commuters can often see it coming, Logan said. A sickout is almost always a surprise action.

"Sickouts are usually short, very short, and they only work if there's an element of surprise," said Kate Bronfenbrenner, director of labor education research at the Cornell University School of Industrial and Labor Relations. "You can't tell the public that in a week you're staging a sickout, because then it's illegal. It's a strike."

While the Muni sickout caught almost everyone by surprise, it didn't seem to engender the same level of animosity as the BART strike or create nearly as much chaos. Many commuters grumbled about the inconvenience but said they sympathized with the drivers.

"I can understand," said Dianne Warren, a 63-year-old retiree who lives in the Bayview and had to wait almost an hour for a bus home on the first two days of the protest. "People don't realize bus drivers have to deal with a lot all day long. Crazy people on buses, loading people in wheelchairs."

Some inconvenienced riders complained that the Muni operators were already well compensated and shouldn't be hurting the public to make their point.

"Their pay and their benefits are already pretty good," said Mary Walls, 38, who lives and works in San Francisco. "It seems selfish they're not willing to contribute to their pensions."

Transit strikes or sickouts are always a hard sell with the public, labor experts said, because most people just want to be able to get to work or school.

"It might not advance your cause," Logan said. "But when you feel you have no other options, this at least brings attention to the fact you feel you are deeply underappreciated."

Bay Area labor experts said the anger generated by transit strikes doesn't seem to have a lasting impact on support for labor causes.

"The population is becoming a little more moderate than it used to be," said Tim Paulson, head of the San Francisco Labor Council. "But I don't see any diminishment in support for labor."

With higher union membership rates than the rest of the nation, and support for worker battles against Walmart and for higher minimum wages, the Bay Area and California remain labor strongholds, Logan said.

What that means for Muni negotiations remains murky. Is another sickout possible? Of course. Union officials, who say they had nothing to do with the sickout, aren't commenting. Rose, the Muni spokesman who was cautious about pronouncing the end of the sickout last week, said the agency doesn't anticipate another.

"Our hope is to continue the process ... and work out a good and fair contract with the union in time to meet the deadline," he said.

Chronicle staff writer John King contributed to this report. Michael Cabanatuan is a San Francisco Chronicle staff writer. E-mail: mcabanatuan@sfchronicle.com Twitter: @ctuan