The surest method would be to remove the tank, take the base outdoors,
and flush/vacuum/shake the nut back to the inlet. (As mentioned
before)

Another thought: If the nut stays near the jet opening when not
flushing, if you have a conventional flush valve, and there's enough
room around the jet to work..

1. Use a loop of stiff wire to keep it out of the jet temporarily.
2. Get about 3 feet of string, ball it up in your hand, (tie one end
off), and let it get sucked through the flush valve as you open it.

(If you're lucky, the other end of the string will get drawn through
the jet.)

3. Drain the water from the bowl.
4. Use a hemostat or other locking grasper to pull the nut near the
opening.
5. Glue the string to the nut with some super glue.
6, Refill the bowl to support the weight of the nut.
6. Carefully pull it back into the tank


--
Email reply: please remove one letter from each side of "@"
Spammers are Scammers. Exterminate them.