I once found a backpack beside the road, in a not very remote area of the UK.
Funny place to leave one, in relatively flat country, and very exposed to theft. It appeared undamaged, so I presumed that it had not fallen from a vehicle.
I observed for about ten minutes in case the owner was nearby, then called the police.
They arrived promptly and opened the pack which contained two large batteries and some cables, no camping or hiking gear.

I never heard how it came to be there, absent minded film crew ?
Stolen and then abandoned, perhaps after removal of other contents?