I was at a performance of In The Heights where Seth Stewart left the show towards the end of act one. He wasn't on there doing Graffiti Pete's bit in the club scene nor was he onstage singing his part in Blackout. The understudy went on mid performance. There was an announcement right before act two started that said "the role of Graffiti Pete will be played by (name of understudy who's name currently escapes me)."
This was during the post show collection for BC/EFA so I asked Christopher Jackson what happened and he told me that Stewart pulled a muscle during one of the dance moves and had to leave the show early.
I have been told that it is not an uncommon thing to happen and I buy that. However, I have been going to the theatre for 15 years and that was the first time that I have ever been to a performance where an actor left mid way through the show.
"If you try to shag my husband while I am still alive, I will shove the art of motorcycle maintenance up your rancid little Cu**. That's a good dear"
Tom Stoppard's Rock N Roll