Mine was fine until he was a few years old also and had some size on it... That when stuff started going missing.
I'm not saying all of them do. However, by by nature they habitually pick. It's what they do and why they are great for flatworms, nudibranch and amphipod population control. If you look close at their mouth they have these pointy little teeth at the tips they use for pyrmalid(sp?) snails, but are also great for getting at hermits.
Also, they are voracious eaters who are constantly on the hunt. This is largely the reason that they grow very quickly. You can't seem to feed them enough to keep them satisfied without a large enough tank with lil' critters for them to hunt down.