This is a pure case of fraud. If you didn't have that feeling to check your machine you would have been a victim. These frausters keep coming up with different strategy to defraud people and when they are caught they start blaming it on devil. You would have raised alarm so that he will be dealt with a little and he will have bitter story to talk about himself.

So my advise to you is, next time you don't have to be carried away to allow your customer to have hold of the machine for a long time because I know that it is not same time that will be spent in putting just the pin and putting another fresh request on the machine. Be bold to request for your machine if you suspect that the customer is taking longer time with the machine.