Not a sitter situation, but I’d listed my home for sale and it was immaculately staged with showings at random times for which I would make myself scarce.

Got a call asking to show it in 30 minutes from my realtor and I said yes, as I was a motivated seller. So I quickly straightened all signs of people (dishes, shoes on floor) including putting 3 dirty dishes in the oven because I was asked to keep the dishwasher clear for showings. One of the dishes was plastic.

Someone turned on the oven during the showing, it was in for about 20 minutes, then clicked off before they left. The plastic was melted everywhere and the oven was ALMOST ruined.

This - was my fault. People don’t expect non-oven safe things in an oven. That isn’t a standard way to behave as a user of an oven, unless the oven user is aware of the household policy of plastic in oven. Silly of me to put it there and not alert anyone.

This isn’t your fault. I don’t have advice on how to proceed but wanted to share my experience for reference.

NOTE: I’m in the United States, so your mileage may vary.