How annoying, there must be a member of staff who remembers it, especially with stuff in it and if you can tell them what was in it.
I got some books from Oxfam a few weeks ago and left them on the bus! In a random twist of fate I had the bus number as I'd noted it to stick up for him in a compliment after he got a load of abuse just for doing his job.
They radio'd and located my books but ended up having to get two buses to the depot (on a big industrial estate) and back and wait around for an hour at reception the next day to get them back, that'll teach me!