Sorry I cannot help you, ebb, except to commiserate.

An idea occurs - did you look around nearby? Perhaps the crack-addled brain figured out that these nice, heavy, round objects wouldn't fetch much at the recyclers, and he tossed them locally after he got over the momentary rage of not being able to find your stash of highly volatile, low solids resin reserved for sniffing?

Best of luck finding the caps, or replacements. Lets hope that whoever the thieves are, that they get stuck in the seventh bolgia of the eighth circle, bitten forever by snakes and lizards...