I think I would have called the police. Especially if I saw a truck with people moving things out and none of the people were the ones that owned the house. Even more so if I never saw a For Sale sign. I'm sure someone in the neighborhood talked to those neighbors.
I got a check for $5,000.00 in the mail a few years ago that asked me to cash the check and keep $1,000.00. I checked the bank, the signature name, address, etc. There was a bank by that name at that address and the signature on the check was from the President of the bank. I immediately called the bank and the law in Texas. They asked me to send the check to them, but void it first. Nope, not doing that. So I told them until I knew for sure what to do I'll just send a copy and keep the original until needed. Long story short, there was a ring of people living in a motel there sending out checks from various banks, they did catch them and I did send the original check and the thugs are serving time as we speak.
Sick people out there. Had I been stupid enough to cash that check I would have had to cover the entire $5,000.00!