OROVILLE, Butte County — On the night Lake Oroville threatened to cascade into town, some of the city’s homeless people were left confused and stranded as panicked residents jumped in their cars and fled in droves.

The homeless people didn’t have smartphones, televisions or radios to tell them that the emergency spillway of the Oroville Dam could fail within the hour — and that a mandatory evacuation was under way. The warning that Sunday afternoon reached a homeless encampment along the Feather River when somebody yelled to them: “The dam is breaking! Get out now!”

They abandoned their encampments along the river, unsure where to go that night. Some spent the night among the city’s dead in a cemetery they hoped was on high enough ground. Others went to a patch of land on the outskirts of Oroville that the homeless call the “Dog Park.”

On their way, they watched as car after car left the city, wondering if they too could find a way out. They felt like they were being left behind to die, several said Wednesday from an evacuation center at the Chico fairgrounds.

“Nobody went around with explicit instructions to help us homeless,” Gary Neely, a homeless man who typically camps along the Feather River, said Wednesday from an evacuation center at the Silver Dollar Fairgrounds in Chico. “I get it. People don’t care. They didn’t think twice about us.”

Some waited five hours for a ride out of town after the mandatory evacuation order came around 4:30 p.m. Sunday. Others did not find a ride until Monday to one of the many evacuation centers — such as the largest in Chico some 25 miles away.

With a new rainstorm adding to the rising Feather River, Oroville’s homeless people said they wonder what will happen if another evacuation is ordered. How quickly will they be able to get out?

“When we see the water rising, we know there’s a problem,” Neely said, explaining how a friend’s cell phone led to his rescue Sunday night. He had his friend’s phone when it rang. “My friend got a call on his phone from someone who wanted to pick him up because there was an evacuation order. Instead they got me.”

And that’s how he learned of the evacuation order. Neely shoved clothes into a red zebra-striped backpack and hopped on his bicycle. A friend offered to tow him to an evacuation center while he held on to the back of his minivan — the vehicle was otherwise full. That’s how Neely got to Chico: sitting on a bicycle without a helmet as he held onto a minivan driving on the highway.

“I'll admit that’s crazy,” he said.

Homeless advocates said it’s appalling. They said city officials should have plans in place to make sure homeless people aren’t overlooked in an emergency, particularly in areas prone to flooding.

“This is outrageous,” said Patrick Newman, a homeless advocate in Chico.

“It’s not acceptable,” said Sister Libby Fernandez, executive director of Loaves & Fishes, the largest provider of services to the homeless in Sacramento.

Shelter operators said the situation in Oroville has led to discussions in their own cities about how they would ensure the homeless are helped during a catastrophic event.

“How do you find them in an emergency? How do we get the word to them?” said Brad Montgomery, executive director of the Torres Community Shelter in Chico near the fairgrounds where evacuees were sent. “I’m hearing mixed results from Oroville. Most of the people got to safety. But others said they were stranded.”

Oroville officials said they were pleased with the orderly way city residents were able to evacuate under high stress after an estimated 188,000 people in Butte, Sutter and Yuba counties were ordered to evacuate. The order came after water resource managers detected trouble with the emergency spillway of the Oroville Dam.

A crater that formed in the reservoir’s primary concrete spillway Feb. 7 forced officials to slow the amount of water draining from the full Lake Oroville. That left the reservoir too full, and water began to cascade over its emergency spillway. It was the first time the emergency spillway had been put into operation since the dam was built in 1968.

The water on the emergency spillway began to rapidly erode the hillside, and officials said it appeared to be on the verge of collapsing, so they ordered the mandatory evacuations. The mandatory evacuations were lifted Tuesday after officials were able to send enough water through the main spillway to lower the lake level and relieve pressure from the emergency spillway.

Stephen Terry, executive director of the Oroville Rescue Mission, which operates shelters in Oroville, said every effort was made to help people out of the city during the evacuation. Terry, a volunteer firefighter with the El Medio Fire Department in Oroville, drove Engine 36 from Sunday to Monday patrolling the levees and helping people.

He said law enforcement and firefighters went through the streets of Oroville with loudspeakers telling people to evacuate, and electronic billboards instructed residents to call 211 for free transportation.

“We offered to help them get to higher ground, and I can’t tell you how many times we were turned down,” Terry said. “There were services. I don’t have a reason for why people didn’t use them, but I have a hard time believing people didn’t know.”

Oroville Mayor Linda Dahlmeier also said everyone who wanted to evacuate was able to.

“Some people chose not to leave,” said Dahlmeier, who was returning from a conference in Atlanta when the evacuation order was issued. She remained evacuated until Tuesday when the orders were lifted.

“I know people were vigilant; they did everything to make sure there was no one in the area,” Dahlmeier said.

For the homeless who made it to the fairgrounds in Chico, it wasn’t that they didn’t eventually find a way out. It was how long it took.

“All this funny stuff was going on around me, so I knew something was up,” said Toni Breer, 51. “No one would tell me where the evacuation center was. I was walking down the road trying to figure out where to go when a bus pulled up, and the driver told me to get on.”

That was on Monday.

For Matthew Perry, 31, the confusion was overwhelming.

“I had no idea what was happening,” Perry said. “I just knew I had to flee. I saw all these people leaving, but I had to wait four or five hours before I could get a ride out. Eventually the California Highway Patrol found me. If it weren’t for them, I wouldn’t be here (at the evacuation center).”

On Wednesday, Perry hunkered under an awning on the fairgrounds with his puppy, Honey. He had new shoes that were a size too big — perfect for wearing with thick socks — and had just showered. Back in Oroville, he lived in a tent with scarce belongings. In the rush to leave, he left all he had behind.

“I just want to get back and see if my stuff is still there,” Perry said. “I don’t have much. But I don’t have a way to get back. I guess I’ll either hitch a ride or walk.”

He looked at the sky. The clouds rumbled just then, and the rain showered down in torrents.

Lizzie Johnson and Melody Gutierrez are San Francisco Chronicle staff writers. Email: ljohnson@sfchronicle.com; mgutierrez@sfchronicle.com. Twitter: @lizziejohnsonnn; @MelodyGutierrez