Has anyone found a foolproof method for securing a mooring pickup stick (tall buoy) so that it doesn't get stolen while you're off sailing?
I guess you're saying that you suspect your stick/float was stolen? That sucks. It always amazes me, the things folks steal. Like potted plants, for example.
The answer is no, 'though your question should have read 'thief proof,' or 'theft proof,' not fool proof. First time you're a victim second time, you're the fool.
The only defense is to secure in such a way that it is so time consuming and inconvenient to take that the thief takes someone else's. Or, per the previous response, forgo the stick and use a boathook, which is what everyone does up here (not because of theft, it's just the way it's done up here).