Used multiple summoned creatures to defeat the Beholders and Elder Orb in the Beholder city in UnderDark. Found nothing on the corpses after the battle was over so I merrily left. Then I remembered that a piece of the Equalizer was supposed to be on the Elder Orb. Returned to the "scene of the crime" but found nothing after a meticulous search. Is it possible that one of my friendly Nishruu's snatched the piece? Anybody know how to get it back?

Nishruus are the most frustrating creatures in the game. I mean next to losing a vital piece or favourite weapon, dying (and getting resurrected) is a walk in the park.
I never use Nishruus or disintergrate spells.

Same thing happened to me exactly,
I used the shadowkeeper editor and just "magicked" myself the appropriate part, hey if things were fair i'd a got it right?.

Thanks for the advice. I've downloaded and used Shadowkeeper and "majicked" myself the final piece of the Equalizer. Don't like cheating, but don't like being "mystically" screwed either.

I don't class it as cheating if you used an editor to get something that ain't where it's meant to be.
You've done the quest, killed the Beholder, so you get the equalizer third I reckon.

Spoiler
.
.
.
.
Look around the dungeon some. Specifically, head north and east whereever possible. On the far eastern side there's a passageway to a cavern in the north (it's all on the main beholder map). On the way, you'll meet some drow, beholders of various levels, and maybe illithids although I didn't see any. The cavern (the northernmost part of the dungeon) has another elder orb (I think) and maybe some other beholders. Check the walls very carefully (go over them with the pointer and look for the open sign). I think there are two or three openings there, one has a few gems, the other one has the piece of the equalizer (note that between here and where you entered you've gotten the good loot. You can explore the rest, but do so at your own risk)

There is no risk at all.I tought this was the easiest dungeon off them all. Just have one fighter with the cloak of magic reflection ecuipped, kill them all. actually the only one who won't kill himself is the elder orb.

masteraleph, the equalizer piece is on the elder orb at the beginning of the dungeon.

Some things stay where they are forever; some don't. Items have been known to vanish if you don't pick them up after a few days, this is supposed to make the game more realistic. If you forgot to pick it up earlier, don't ruin your game, just cheat it in using Shadowcheater.

Desdicado, I have to disagree - cheating is cheating. What I don't understand is why people get so hung up and have to justify it, or call it another name. Enjoy the game - do what you have to do, you're not competing against anybody but yourself anyway and nobody's going to be disadvanteged if you cheat an item in that you feel you should have had!