I got briefly separated from a group once - the group I was with overtook another, and for some reason I ended up in the middle of that one, thinking it was ours! My own fault, wasn't concentrating and assumed the lights and bodies all around was still my group. Luckily a lass in our group realised what had happened and trotted back the few yards to kick my arse into gear. Could've been a lot worse and shows how easily it can happen with a simple lapse of concentration at the wrong time.