I don't have any direct experience with this, as I have never connected in PTY. And I don't know the CM policy.

But I will say that in a dozen years of regular flying in and out of PTY, I have never had any luggage losses. Also, in the carousel area, there are always dozens and dozens of bags taken off the belt and stashed to the side, accessible to anyone. I have glanced at the tags a few times, and I suspected those were connecting bags, as there seem to be way too many than just lost or misconnected bags. There are airline people about, but none seem to be specifically guarding the bags. Frankly, anyone that were so inclined could seemingly could just take one of their choosing. That they are unguarded, to me, is a testament that they are safe among passengers and workers, and possibly more safe than out of sight in the baggage handling area.

A call to Copa may give you the official policy on how your checked luggage would be handled on that layover. I would be very, very surprised if an agent could describe to you the security precautions for bags connecting overnight.