Dude. If you still want the job, you really had no obvious part in the disrespect, and the owner wasn't part of the immediate rage firing, give it a day, let it cool off, then go see the owner directly.

Just be straightforward and honest, speaking as his equal (because you are): "I meant no disrespect, I really was just there and not a participant, I understand offense was given, but that was not my doing or intent. I liked this job, I enjoyed doing it, I thought I was doing well at it, and I can't believe it's gone just because I happened to be in the same room when this happened. Is there any way this outcome can be reconsidered, or is it set in stone?" Professional, straightforward, calm.

If the owner wasn't a part of the direct confrontation you might be able to change his mind. I'm saying this because if I were your manager, the way you wrote your text would make me at least question the decision, and I'm hard to convince. People do shit in indignant rage they regret later, restaurant kitchens are wild places anyway, and I don't know this guy and I don't know you, but if you want that specific job back then it's worth a shot. Good workers are worth keeping.

But you may not want it back. If not then just ignore this, chill for a day or two, and start looking for the next thing. Whatever you decide I hope it all works out for you.

Sounds like might be worth talking to a lawyer on that one

Man wtaf. Why would you even want to commemorate that and then fire people for talking about it. “Enjoy your burger, it’s a memento for the most traumatic day of my daughter’s life. Why no she doesn’t ever eat here, why do you ask?”