I live in Nevada and collect Social Security Disability. I received a Grant check in the mail for $500.00. I took the check to my bank and asked them if they could tell me if it was good. They made a phone call and came back and told me it was good. I then cashed the check and received the $500.00. It turns out that the check was NOT GOOD and so when my disability check came in the next month, the bank kept the money. Is the bank allowed to keep my SSI money?

They probably can. The bearer of a bad check takes the loss no matter how far the check goes before bouncing. Why was a grant check bad--paid by mistake and payment stopped? You had concerns that it might be bad?