[EdenSlate]

Correct assumption, better odds involving Paypal at the return step than DNA (i.e. exploiting their weakness).

Imagine the claim from PP's P.OV.
They only have two verifiable data points : tracking showing delivered, & its weight.

In order to prove you boxed them, store would need to provide an uncut video footage of the delivery process.
From receiving the package from driver's hands, to unsealing it (if there was a seal in the first place) & emptying its content.

Even then, I think there would be plausible deniability for you to argue the evidence was tampered.
At this point, it would most likely be about pushing PP reps hard.