I don't know about abusive - certainly embarrassing, and as you say, its her fault she left it on the bus, she's old enough to make sure she's got everything before getting off the bus and to be responsible, and she's learnt her lesson.
There isn't 'official' PE kit, apart from the top, but they let her wear her school shirt so she wasn't literally in just her underwear. I just don't know where I'm going to get a pair of shorts for a couple of pounds before Friday. I'll have to ask around and see if I can borrow some.