Which is exactly what you should have done. Unless you're very new to the game, everyone knows that those 2 rooms are skipped. It happens, usually because someone engaged something, it's no big deal though. I'd have told the RPR, politely, to stop being a baby. It was their error, not yours.
Sounds like the RPR maybe didn't know the content well.
I love when people give sass in cutters cry and then eat everything and/or die to Chimera. Its one of those dungeons that can put people to the test after they've given mouth. Had one of those a little while back when levelling GNB - was my 3rd time playing the job which I said in chat. A few wipes and quite a few deaths which the healer and one of the DPS tried to put on me. While I was new to GNB, and probably not perfect, I could tell that something more was off. They were just eating everything, and I was having to kitchen sink constantly.
I ended up solo'ing Chimera from 3/4 health and they left promptly. I wouldn't take it as them shading you, or care if they did. I'd say they know damned well that they were the problem so are getting out quick. And if not, well, they're deluded and not your problem.