Did you ''snail mail'' a check? A postal money order can be tracked..if by credit card or Paypal--these can also be tracked. I think I would pay for the items again if you're positive they never got payment, and wait to be reimbursed when the orig payment arrives. If it never does, a check never cashed will never debit your acct. The person sounds honest, so I think they will return your money whenever.
I get so annoyed with my mail carrier--she drops our mail at wrong boxes all over the neighborhood, and we get other peoples' mail, as well. To forestall it being wrongly delivered again, we deliver ourselves. Sometimes it looks important. She is nearing retirement, and we look forward to it. LOL Numerous folks have complained to the office, but she's still out there!! So your mail could have gone to the wrong box and the recipient just trashed it.