Hi OP here, so, first of all I would like to know who voted "Yes" and "Other" lol.
Just to answer a few things that have been mentioned:
Grandma does not have a key, my son let her in. (Because why wouldn't he? He didn't know he was about to be strong-armed out of his tv!)
As for my husband he was at work, and in fact with the long hours he is working this week (he is management in a workplace currently dealing with a strike) he wouldn't have even had time to deal with this until , well, who knows when, and I wasn't willing to wait. He was fully on board with me taking the TV back though.
The people that helped her take the TV were the two adult sons of her next door neighbour. They help her out a lot with various neighbourly things, and from what I have seen of them in the past, seem like fine young men. (That's why I tried to give them a neutral sounding name like "helpers", rather than "henchmen" or "goon squad" lol.) I am sure they simply thought they were being kind by helping her move a TV. I don't blame them at all!
I don't believe there are cognitive issues, only boundary issues. We don't have her dog sit when we go away anymore, due to issues like rearranging our furniture ("doesn't it look SO MUCH BETTER like this?") , reorganizing our drawers ("They were just SO MESSY. I have sorted them by colour!") (I hate that she touched my underwear lol) and trying to "help" by getting rid of things from the garage and basement ("I brought 6 garbage bags of your stuff to the dump! Don't worry I only brought stuff I didn't think you needed!"). I mean she is not constantly like that, these are three things that have happened over like 20 years and they have been shut down each time...So this doesn't exactly shock me, although it is a new low. We usually just laugh and joke that she is a sitcom mother-in-law, but this one was too unfair to my son.
As for me being the "bad guy", yeah, there are rumblings of that. Apparently she is very hurt?! Hey, if any one takes her side they can let her take their TV, have at it lol.