Great question and great story idea! you will have to post a link to it once it's done.
Ok, I've been hosting 3 places for 2 years now so I've pretty much encountered everything. In addition to the ones already mentioned....
1. Rearranging furniture and moving artwork. I have found a small painting I keep on my dresser placed in and next to the dresser multiple times.
2. Breaking things and not telling me. Have found broken dishes in the garbage a few times.
3. Overflowing garbage, especially bathroom (EWWW) (even though it's in our rules to take out your own trash).
4. Bleached pillow cases from acne/facial creams!! Not only does it ruin the pillow case it also ruins the other items in the wash. A fellow host I know included, "no peroxide facial products on her house rules", LOL.
5. Arriving early even though I clearly state in my rules and again in my day of check-in instructions letter that we will not accept anyone until after 2:00 pm.
6. Finding that someone had a potato chip fight in the apartment. No but really how else can there be crums in every room in the house.
7. Guests who want 24/7 concierge service yet decided to rent an airbnb. I love hosting but I have a life. If you use 10 rolls of toilet paper in three days there is a grocery one block away and I will even reimburse you. But seriously I did my part by having a fully stocked tp drawer.
I could go on and on but I don't want to seem like a complainer. I love my job and I love hosting. : )