On our first trip in 2007 we ended up hanging out with a great guy by the name of Dennis. His sitch was that his new girlfriend bailed on him and the trip days before leaving. He was so fun to hang out with and even though we were a couple and there for the first time, loved involving him in our fun. (i.e. hung out at sexy pool, had dinner with him one night, etc. etc. etc.) and it wasn't just us, many people, couples, groups, etc. befriended him; not because he was alone, but just because that's how TRC is. You'll have a blast!!!
Ahhhhhhhh that totally sucks and is quite rude of your friend to do that. I know you'll still have fun. Go and enjoy.