This isn't so much an AIBU but I didn't know where else to put it.
I went to pick DD up from nursery today with FIL. Her room adjoins another room and the toilets which are in the middle can be accessed from both rooms (although I didn't know this). I went in to the room but realised there was no one in there as they were out in the garden so I grabbed DDs bag to go down to meet her. As we were leaving there was a girl who came out of the toilet, in to the empty room with her trousers and knickers down looking a bit lost. I popped in to the room next door and spoke to a member of staff to let her know that there was a child in the unsupervised room and she looked in, said "oh yes, she's from our room, the toilets are joined" and just went back to her room. The little girl was still standing there with everything on show looking bewildered.
I know that every child can't be supervised when they go to the toilet, but surely when it's pointed out that there's a half dressed child going the wrong way the staff member should have at least gone to check if she was okay. It's not like anyone can walk in as you need a passcode to access the building but it's happened before that someone leaving has held the door for me to go in and I didn't see a staff member between entering the building and seeing this little girl. It does raise a slight concern about security. So, AIBU?