Here's something on the N.Y. law from 2013
Cuomo Acknowledges 7-Round Magazines Don't Exist -- NYMag
So, it's not very likely that your dad HAD to sell his comp guns or move out of state to keep them.
What's "a total knee" ? He got sick and entered
the nursing home is a very vague thing to say. He likely had his knee operated on and was layed up for what? six or seven weeks recuperating where he had access to physical therapy. The sheriff came to his home and took away is guns
for six or seven weeks?
Something's wrong or very incomplete with that story. If he wound permanently housed there due to physical incapacity and perhaps age, then scenario one applies: he wasn't coming home again and there was no family members to take over his guns, so the law took them. There can't be any other explanations for it, even in New York.
Again, the cops won't take someone's gun away who's just recuperating for a few weeks. And an abandoned car WILL be towed away after a few weeks if it's not regularly moved and there's nobody available to take charge of it. So, sorry man, but something's goofy with your examples.