We sympathize with you also! We've lost 3 caches out of the same city park - we've now placed our last and final one at that park because it's obvious that the kids destroy them.
Our first one had an emotional attachment - we set it out specifically so a little friend of ours with leukemia could walk far enough to find an easy cache. She found it and was thrilled - but it was destroyed within a few months afterwards.
The second one was special because it was the State's "Happy" cache and we worked long and hard on special camo for it - gone in a few months.
The third was a simple micro - when it disappeared it was "So what else is new?".
This last one is hopefully something the kids won't look for! If it disappears we chalk up the area and keep hiding them somewhere else.
Frustrating to lose one - but heartwarming to see one that lasts for months and months! Keep hiding!
"Be kinder than necessary, for everyone you meet is fighting some kind of battle."