@Melissa1401
I am very sorry to hear of your experience, which sounds very distressing indeed. I also think it very wrong that Airbnb made you go through the whole process before telling you the deadline had passed.
I am probably one of those hosts who are too trusting in that, although I am usually here, I have sometimes left guests alone in my house when I've done away on work trips and I also do not have things locked away.
However, I've not left them for long periods of time, am usually back before they check out, there are other guests staying here (at least one long-term guest whom I trust), often a cat sitter dropping by twice a day, so no one is completely alone to do as they please and I also vet guests very carefully before they come and make sure to meet them on check in.
You story still serves as a reminder to be careful. @Helen3 is absolutely right that you should have a co-host or someone else who can check up on things while you are away. I would suggest always inspecting the listing as soon as possible after the guest checks out.
Could you pursue this further with the police? I have no idea how effectively the French police deal with such situations. From my experience (not Airbnb but other incidents of theft, property damage or personal assault), the police here would not pursue the matter very far. They simply acknowledge it, ask a few questions, fill in reports and then move on...