A guest ignored my instructions and broke the front door lock on his way out. I only realised a while after he left that I was trapped inside the house (the window at the front has a security grill so you can't get out that way) and tried to message him but he didn't respond. I had new guests checking in shortly.
Luckily, I managed to flag down the neighbour as she was leaving her house, pass the key through the letter box and get her to open the door from the outside, but it meant I could not close the door again until the locksmith came.
The new guests arrived and I explained the situation to them. I showed them around while keeping an ear on the door to make sure no intruders entered! Meanwhile, the guest who broke the lock returned and, having not read his messages, closed the door and locked all of us in!!
Luckily, the new guests were understanding and the locksmith came quickly to replace the lock.
I am not sure what I could have done to be better prepared for this situation (all guests are instructed how to operate the lock and this guest broke it through brute force and sheer carelessness) but it's useful to have a few locksmiths' numbers to hand.