Oh noooooooooooooooo! Hoo boy!!!
There IS a good chance that it's still in the tank...pumpouts lose their "oomph" once the level gets below the top of the discharge fitting and lets it start sucking air. If your tank has a 3" inspection port, just put on some rubber gloves...smear some Vicks under your nose...open it up and reach to fumble for it (If your hand is too big to fit, someone with a smaller hand will win the honor of doing it). If it doesn't have an inspection port, it's neither expensive nor a major big deal to install one...and you should have one anyway. Beckson makes retrofit kits that West Marine sells for as little as $10 or even less...and all you need is the correct size hole saw and access to the top of the tank...you shouldn't even have to take the tank out. So if it's in the tank, finding it and getting it back is a bit of a nasty job...but not a difficult one. Trouble is, it may be in the plumbing somewhere...not in the tank at all....Wait a minute...a possible INSPIRATION!!!!Before you look in the tank...have you disconnected the discharge fitting on the toilet to see if just MAYBE it didn't make it past the joker valve?Also check her clothing THOROUGHLY...amazing how things can find there way into a cuff or a pocket without our knowing it.