lost package?

Dear Internet, I need your help.
A package wound up in my mailbox, or rather what was left of a package. It was something I mailed in early November (single digit date, but it’s blurry so I’m not sure if it’s 2,3 or 8), but it is torn open and the “to” address label was ripped off. The tape also took off the last 4 digits of the delivery confirmation form. Obviously, the package is empty.

I can’t believe someone who ordered something from me over 3 months ago wouldn’t have contacted me about not getting it, but short of someone finding the envelope and putting it in my box as a joke, I don’t have another explanation. Maybe it was a gift, and the sender doesn’t know it never got there?

From the size of the padded envelope, my guess is it was a sweater, or pj pants, or maybe a couple of scarves.