Repeats

I have a list of 'fillers' that have been tried and tested to get a laugh. I could not understand though, why one of the best tags I used on Saturday at Thorpe, only got a mild titter!!! I found out last night at the Oak. It turns out that whilst I was out at the khazi, the chap performing on the Compton had already used it!! Must say the audience were very polite though in giving mild appreciation to something they had already heard? How embarrassing.