Before I start, this isn't a thread about The Lighthouse Family or their seminal 1995 album, Ocean Drive. So apologies for that.
http://www.chortle.co.uk/news/2010/10/04/11858/ronnie_barker,_ideas_thief%3F
What do you do, if this happens to you?
A few years ago, I wrote a sketch for a topical show, which got rejected. Then, when they compiled an end of year show, my sketch turned up, almost word for word - but I wasn't credited.
Although I felt vindicated because I felt my sketch was good enough to get on originally, I also felt robbed because I didn't get a credit. In the end I just let it pass, mostly due to the fear of being blacklisted for accusing someone of something. However, if it was now, I would kick up a minor fuss, forward them the e-mail showing the exact time I sent it, etc.
I also wonder why it happened - maybe they remembered the sketch, but not who wrote it.
I should say that I've generally found that shows are good about giving you a credit for ideas, even if they've gone on to completely reinterpret your sketch.