CacheARRRS: I put out the replacement cache, and it had disappeared the next day, before I could even activate it again! Obviously this one has drawn the attention of a muggle, since it was secure and fine for a few years, but I have lost three of them in the last few months.
This cache required special camouflage that wasn't too expensive or time consuming, but expensive and time consuming enough that I don't want to keep replacing it. :(
I'll try and cook up a new one nearby that might fool the cache-thief for a while.