Upvote:1
If immediately you meant, by left and came back, there is a chance that you just gave someone free gas. If you haven't left yet or no one has used the pump, the credit will still be there and you are still entitled to either your money or your gas. If someone pumped it, it's really up to the store, It is up for debate, because it could be construed as you prepaying for someone else, or being generous (in the ex.: paying for the next person in line). Gas stations are usually owned by a single person and they don't make much, talk to them and don't be a jerk. They don't make much money off of gas.
Upvote:3
Ask to speak with the manager, show your receipt, ask them to check the cameras, most likely the credit is still in their computer system.