I myself wouldn't worry about losses either, using your numbers. But if you're returning the product in 2016, then it's still "sold". The fact that you sold it back to the supplier for the same price you paid for it, doesn't affect things. What I would suggest (and it's just a suggestion) is that if Mary Kay will not be sending you a 1099-MISC, I wouldn't bother reporting it. Not exactly "legal" per-se. but if the IRS were to audit you, I serious doubt you're going to jail for a loss. You could be fined for not reporting/filing it though. But again, looking at your numbers, I believe the IRS has bigger fish to fry.
