Peaceful monsters don't pick up objects, so the hobbit didn't get the amulet from its Elbereth spot. Your pet may have picked it up and dropped it elsewhere. Another monster may have picked it up afterwards, or it may not: check every square of the level. Also, an Elbereth-ignoring monster (mostly @, in particular werecritter in human form and elves) may have picked it up and even worn it. It's even possible (albeit unlikely) that a monster picked it up then fell through to another level. The amulet may also have been eaten by a rock mole, rust monster or xorn.

To answer the titular question (even though the hobbit probably doesn't have the amulet), a nymph or monkey can steal an object from a monster without risking killing it. A monkey basically has no chance against anything; a nymph against a hobbit is a fair proposition. A nymph will wear the amulet. You can use conflict to make a hostile nymph try (beware that it may get killed instead). You can tame a nymph; it may kill the hobbit. You can polymorph into a nymph and use your #monster ability.

Of course, the easiest thing would be to kill the hobbit. If you really don't want to do it to maintain your out-of-game alignment (the in-game penalty is too small to consider), you could let your pet do it.

Peaceful monsters don't pick up objects, so the hobbit didn't get the amulet from its Elbereth spot. Your pet may have picked it up and dropped it elsewhere. Another monster may have picked it up afterwards, or it may not: check every square of the level. Also, an Elbereth-ignoring monster (mostly @, in particular werecritter in human form and elves) may have picked it up and even worn it. It's even possible (albeit unlikely) that a monster picked it up then fell through to another level. The amulet may also have been eaten by a rock mole, rust monster or xorn.

To answer the titular question (even though the hobbit probably doesn't have the amulet), a nymph or monkey can steal an object from a monster without risking killing it. A monkey basically has no chance against anything; a nymph against a hobbit is a fair proposition. A nymph will wear the amulet. You can use conflict to make a hostile nymph try (beware that it may get killed instead). You can tame a nymph; it may kill the hobbit. You can polymorph into a nymph and attack the hobbit; this automatically triggers a steal attack in addition to a hit, and I think the hit won't kill the hobbit if you're unarmed and have no bonus (but I'm not sure about how much damage an unarmed polymorphed player causes).

Of course, the easiest thing would be to kill the hobbit. If you really don't want to do it to maintain your out-of-game alignment (the in-game penalty is too small to consider), you could let your pet do it.