What positives came from the rehearsal? They said that you can play so that should tell you that wasn't the issue and help your confidence.
Also you've learnt to be not too denigrating - maybe your comment should have been "great, my slapping is a bit rusty - that'll give me a chance to get my slapping back up to par". Shows you're keen and willing to learn.
As @Old Horse Murphy suggested, maybe the other fella doesn't work out and they'll come back to you. You'll be in a more powerful position then.
Good luck.