I always find these "caught" threads a bit disappointing. Mostly because they nearly always just turn out to be someone being spied on.
In British English, the more common interpretation of "caught" implies that someone has walked in on the subject in the middle of a dubious activity - in this case, having a wank. I find those much more entertaining, seeing the response from both parties - does the caught individual frantically cover up and/or scuttle away or does the catcher sit down and join in with the activity?