When in the forces we'd normally only left the bandroom a few minutes before someone would be flapping that they'd left something behind. A 2-3 hour coach journey can seem much longer when you're panicking whether you've got your shoes/plume/bearskin with you! - On several occasions my colleague on tenor sax got away with playing a concert in his brown shoes, just making sure he kept out of the way of the Band Sergeant Major.
Most awkward one for me was quite a small one really, when I turned up for a guard-mount without my lyre, that was at home with my own instrument, rather than the band one I'd picked up that day. 9 times out of 10 it wouldn't have been a problem, but it was not a good day from the band's point of view, with mistakes left, right and centre, whereupon the MD spotted I had no lyre, resulting in several weeks additional afternoon practice sessions in the bandroom
The most potentially disastrous one was when I was going away with my wife for a weekend, taking the saxophone with me, only to realise I'd left it on the train. Leaving wy wife with the rest of the luggage, I got to the barrier just as the train was departing from the station, so although I managed to get back on it, I had to stay on to the next station before I could retrieve the instrument and take the next train back. It certainly shows how lax security is, in that nobody had spotted/reported it, and it could easily have been quite a powerful bomb left there :shock: