You take the packet of crisps and the mars bar to the counter.
The man smiles at you.
You say, ‘Hi,’ to the man.
The man doesn’t say anything.
You put your hand in your back pocket for your wallet and realise that it isn’t there.
You say, ‘I’m really sorry about this but it looks like I’ve forgotten my wallet,’ to the man at the counter.
The man doesn’t say anything.

do you:

tell the man you’ll be back in a minute and go and look for your wallet

just give up and go home