I am so sorry your mom was scammed. These scumbags will pay sometime in the future, but that doesn't help your mom right now. I hope that was not her food money.
I had an elderly aunt and uncle who were scammed by people saying they would put a new roof on their house, but needed a $2,000 check up front to buy supplies. One guy got on the roof and pounded a little bit, then left.
By the time A & U realized there was no roof going on and called the police, one of the guys had already gone to the bank and cashed their check.