I have done this myself on a 717.
There is not enough room to intentionally get it past the other nipples.
Nothing for it but to correctly identify where it lies, and remove the nipple adjacent to it, pop the spoke out of the hole and it should be okay.
If you are confident with wheels forgive this next bit, if not I hope it helps.
You don't need to worry too much about doing this:-
After replacing the nipple on the spoke (not dropping it into the rim
) just wind it up 1 full turn at a time at first until you feel a little weight, after each subsequent wind grab the spokes all round the rim to 'tension it'. Every few turns spin it round in the frame to check how true it is.
Once it gets tight start to turn the nipple half a turn at a time, tensioning between turns, spinning every time. Touch no other nipples, the wheel will eventually true up and you will not have ruined the integrity of your wheel.
First time you ride it it will ping, this is normal. After the first ride check for true, correct if necessary, job jobbed.
Somerset, like 'Heartbeat' with newer cars!
Retro MTB: 1992 Cannondale 3.0 Deore XT M730. 1992 Marin Pine Mountain Deore DX M650.
Retro road: 1992 Eddy Merckx Corsa Extra Telekom Shimano 600 STI. 1993 Dyna Tech Ti.
Modern: 2006 Wilier scandium Ultegra 6600. 2014 Wilier GTR Ultegra 6800.