[mothered]

Should I wait to see their evidence before I make the push for an escalation? Or push anyways, while they retrieve it?

Escalate It now.

Their assessment will also be based on the evidence that you've requested.

I think they’ve probably thrown it away at this point. Would they have the capacity to retrieve it after days(+)? & would this help with the claim?

Whether they can retrieve It or not, Is not your problem.

You want your Item back, and that's the end of It. In terms of the claim, they've disposed of the wrong Item you've (seemingly) received, so tossing It In the trash works against them.