No, it's not a mistake. It's clearly a change of mind.

I try to see it as I would a B&M shop. I have something in my hand, I have told the salesperson I am buying it, I get to the counter and, seconds before I pay, I change my mind and leave it with the person behind the counter.

I also try to see non-payers as two different groups. Those who don't say a thing and don't react to any messages... just never complete checkout, and those who take a minute to let you know they've changed their minds.

It's just not the same, though, is it?

Anyway, them's the breaks. In the next few hours the item will be eligible for a non-payer's dispute. I will log it in and they'll get their strike.