I'd personally delete the log of a Throughdown (of the person who tossed it down) if the original was there, but not punish those who followed. After all it wasn't there fault.
If I believe a container is missing, I'd first try to contact the owner and I'd DNF it. I've done that with a couple of the posters above :-)
But if I see a destroyed container, I'll take a picture - reassemble the best I can, and if it's not possible, and I have something reasonable, I'll toss it down. But follow up with pic's to the owner. I've only down this once, usually when I find a container like this, I'm no place near my car which has the stuff to replace a cache with.
Right now I've got an upstart w/ 39 finds who seems to think I should go out after his single DNF to check my cache since he/she couldn't find it. Yesterday (six days after his DNF of the cache) he posted a needs maintenance on my cache. I'm pretty sure it's still there, it's just not a traditional container, I'll be checking that this afternoon.
So another question, would you post a needs maintenance on a cache that you could never find? And also, if you go out and find that it's safe an sound would you delete their Needs Maintenance log?