If the issue are tent stakes/lag bolts which get buried under surface, clear solution would be metal detectors available to borrow/rent (or brought by each camp). Also probably could do a drone or ground robot with a metal detecting loop on the bottom.

The best solution I know of is to get three-link segments of chain and put one on each screw as it goes into the ground. That not only marks the spot, it also gives you a flexible attachment point which is useful in all sorts of situations. (Two links would be pinned in a stationary fashion.)

Biggest problem is it’s a pain in the ass to chop up all that chain, and nobody sells them in pre-cut lengths.

Or just count them before and after. Know how many you're supposed to bring home.

The problem isn't that there aren't solutions, the problem is getting everyone on board