I received one that was extremely legitimate looking that listed the companies I would be shopping using their logos and everything. I already shop many of these companies. I knew contacting local law enforcement was a waste of time. I handed the check and accompanying letter over the manager at the local Union Bank as that was the bank the check was written on. He assured me it would be forwarded to their fraud department. He said they get their fair share of people ib their trying to cash the checks.
On a side note, my bank is a tiny little country bank in the middle of nowhere. Despite having cashed thousands of dollars worth of checks with them from mystery shopping companies without a single one bouncing, every time I go in, the cashiers ask me, "Are you familiar with this company? Are you sure it is legitimate.". They will not believe me that mystery shopping is a real business.
Recently I had to pay for something and was not comfortable using my personal checking account. Dummy me opted for a money order instead of a cashiers check. Of course the payee lost it.
It was purchased through Western Union and I had to go through the claims department. Western Union sent me a $400 refund check written on Wells Fargo. My bank would not cash (yet they cash all my Podunk mystery shopping checks) because they were convinced this was a mystery shopping scam. I assured them it was part of my consulting business and not my mystery shopping business but "Western Union" spooked them and they would not cash it.