I will say on some gift cards I've bought before the scratch off material is on a piece of plastic? or some material unlike actual scratch tickets. I have definitely pulled off the scratch portion on gift cards before. Sometimes I've tried to see if I can get it off without having to find a penny. However, if I recall I don't think you can even access the scratch off portion without tampering with the paper holder the card is in? but I forget.

Regardless I think one should see some signs of tampering if the scratch off was removed in some fashion.