I had this situation when I was on a school trip to England, my first trip abroad.
We were staying with host families. One evening I went into the bathroom to do my business. I flushed the toilet, but it wouldn't stop. I panicked, and after consulting my classmates, who also had no solution, we all went into the living room, where we were greeted by an unpleasant sight - our overweight host lying on his sofa, covered only by his white underpants.
We told him about the problem and it turned out that you had to open the tap on the sink to stop the toilet flushing. I felt so bad because it must have meant that I didn't wash my hands, which only happened because of the panic. So yeah, pretty embarrassing.