Ooo, I hope your burger was good.
I'd think people would be able to tell a male from a female without having to shave them, even if they'd already been altered. I get that people want to keep overpopulation from being any more of an issue (hence why all our animals got spayed or neutered within the first two weeks of us having them), but he clearly has a home. He lazes in the yard all day, and we feed him, and he comes inside at night.
I guess it was just one of those things. Nothing like this has happened in 9 years to him, until the new neighbors moved in.