Free shirt but reasonably minor moral issues

[Rupert]

So I felt like semi-ballin' today and went to River Island to binge on clothes and [censored]. I got 2 shirts, some trousers, cufflinks, and a tie. The dude on checkout was a bit dumb and he forgot to scan one of the shirts and since he looked a bit douchey I couldn't be arsed to point it out to him and I got a free shirt (£30). Total bill was like £87 so he shoulda noticed really.

Should I have told him?