LeBeouf was there for his film Nymphomaniac. Obviously, someone put a gun to his head and made him attend, because otherwise he would have stayed home, right? Since he said he wanted to retire from public life and everything.
That's why LaBeouf behaved in ways that wouldn't draw attention to him at all. First he went to a press conference with his co-stars, only to leave 10 minutes in. The only thing he said was something someone else said: "When the seagulls follow the trawler, it is because they think sardines will be thrown into the sea. Thank you very much." (French soccer player Eric Cantona said this in 1995 during a press conference after he kicked a fan in the head, a level of badassery to which LaBeouf can only aspire.)
His co-stars laughed as he walked out, either thinking "Oh, Shia!" or "Oh, Shia, I cannot wait until this publicity tour is over and I never have to see you again."
LaBeouf then appeared on the red carpet wearing a paper bag over his head with the words "I am not famous anymore" carefully written on it, where he posed for several photos at various angles like most non-famous people do.
Earlier today, LaBeouf's director, Lars von Trier, foolishly tried to upstage LaBeouf in a photocall by wearing a T-shirt that said "Persona non grata official selection," a reference to that time he said he was "a Nazi" and sympathized with Hitler "a little bit" at the Cannes film festival. Cannes then pronounced him a persona non grata.
I'll bet the set of Nymphomaniac was so much fun.