Dang that's a shame, the M66 is my favorite .357 Mag. You did report them to the police I hope?
I had a some what similar incident happen to me. Not long after moving here back in '94 I had some folks install a garage door opener in the garage. At the time I kept my bow on a rack in the storage room you reach from the garage. Months later really I walked by and the door to storage room was open. Normally it's closed. I noticed my bow missing. Looked high and low but never found it.
Since the garage door has always been and still is kept closed and locked unless we're outside it had to happen while they were there. But I didn't know it was missing until months later and there was no way to prove anything. I did report it and there was a hand print on the wall where the thief had braced themself when reaching to get it. But no use able print was there.
Sure miss that bow it was a real favorite of mine.