No one is perfect but you don't need to lie....

Speaking from a position of seller and buyer... It's up to the individuals to make things work. As for me... I would not be surprised if some of those boxes were stuff for me. I know I've totally forgotten about agreeing to pay before. It happens - had it happen to me as a seller too. So I send a reminder, and honestly I'd hope someone would do that to me if I "bone" them unintentionally. These are old car parts. Nothing is really that important in the big picture except mutual respect of the participants.