I had the same exact scam happen to me on Mercari for a very expensive sony camera lens, sent to my neighbors with a tampered shipping label. I believe this is a very common scam.

I did file a complaint with Mercari immediately when the package was marked delivered.

Mercari said just wait, give usps a chance to deliver it, don’t worry.

Luckily I talked to the mailman, who said he delivered an item to my neighbor with that tracking number.

I managed to recover the package, a roll of decorative vynel sheeting, close to the weight of the lens I ordered.

I took photos of everything and sent those to Mercari. I believe that if i didn’t recover the package and provide evidence, Mercari would have said tough luck and the funds would have been released to the seller since it was marked as delivered.

So yes I believe the sellers story