@Rebecca1234
Well, it's obviously too late now. The guest is just another "problematic" one, and you'll probably just have to take this one on the chin.
Just out of curiosity, what's with the "double flush" thing? Are your toilets not functioning correctly? If not, you really should get that fixed. It's one of those things this type of guest looks for. In their (convenient) assessment, it could be considered "not working", and a "non functional toilet" could be construed as just as serious as "no water" or "no electricity". Even if it's a gross misrepresentation.
These things can be wildly exaggerated. Especially if there's a reward.