Originally posted by jonnin:

I am seeing some oddities in my unmodded game. Necks don't drop tails for me much anymore, is one. I don't know about eyes, I toss 50 at a time to odin and try not to pick them up, so I haven't noticed.

0 star necks only have a 70% chance of dropping a tail. That could just be bad rng and not paying attention each and every neck kill. 0 star Greydwarves have a 100% chance of dropping 1 resin, 1 rock, and 1 wood and a 50% chance of dropping an eye.

OP didn't specify if any mods are in use but a bad run of rng could explain few dropped eyes but not the disappearance of the stored ones.