Did the guests leave the heat on when they left and it was on for 3 weeks before you checked on it? If so, you need to have someone in the neighborhood go in to the unit and check on everything after each set of guests check out. You cannot trust the guests to leave the unit in the condition you tell them to or to report problems to you accurately. Anything could be happening without your knowledge.
Did the guests steal clothing? If they are thieves then it is unlikely they will return stolen items. You would need to threaten them with involving the police and even then it is unlikely that you will ever see those items again. If they admitted in writing that they took things you could try billing them through the resolution center and see if they will pay to avoid a police report.
If you are an absentee host you need a cohost at the location to walk through at check in and check out or to go in right after check out and make sure all is well. You need to securely lock personal items in a strong closet and the cohost will make sure that the guests did not break into it during their stay.
Your listing is a private room but it looks like you are not present. It is also very cheap. You should list it as a whole house and raise the price. The pictures are terrible, much too dark. Do you cook breakfast for the guests? If not you need to change the description. House rules?