ST. LOUIS — For beleaguered Rams fans, it was the happiest of celebrations: Last month, the team that won the franchise’s only Super Bowl title gathered for a 15th-anniversary reunion. Marshall Faulk, Kurt Warner and four dozen other members of the Greatest Show on Turf were bathed in cheers from fans who have watched a lot of losing teams since that magical season.

But when their coach, Dick Vermeil, thanked the team’s owner, Stan Kroenke, for putting the party together, he was showered with boos. A multibillionaire with a flair for staying in the shadows, Kroenke has become a bogeyman to Rams fans who fear he will move the team back to Southern California.

There is no shortage of omens for those in search of them. When negotiations between Kroenke and the regional sports authority over renovations to the team’s stadium stalled, the team reverted to a year-to-year lease. Kroenke bought a big piece of property in Los Angeles, where two other real estate groups hope to build stadiums to lure a team. Kroenke rarely speaks to the news media, and his silence, some fans believe, means he has made up his mind to leave.

The reality is that no matter how much Kroenke may want to move to Los Angeles, he cannot leave St. Louis without the consent of the other 31 N.F.L. owners, who will weigh many factors, including whether the club has engaged in good-faith negotiations with the local community.