Ok..lol, wow...
I still say
Toon Gemini Elf's summoning part is a condition rather than a trigger, however it could be both for all we know. For just this example's sack, let's say that it's both. >_<
If you
Magic Jammer,
Solemn Judgment,
Magic Drain (And they don't discard) or any other means of negating a
Soul Exchange and
Last Will. Do the conditions they make vanish as well? Of course they do!
So if
Skill Drain negates effects resolving, then that means whether or not Fusilier was summoned via Tribute or Normal summoning doesn't matter, it's effect was negated and there for if
Skill Drain leaves the field it won't reset because the action of it being summoned hasn't happened again. (By Reset I mean reset back to the stats it was summoned such as 1400/1000)
This should apply to
Toon Gemini Elf as well. If you negate the effect (which off it is after thinking and getting rest on it) I'm pretty sure the same occurance will happen here.
Skill Drain negates the whole effect from resolving, at that point the effect of
Toon Gemini Elf would reset after
Skill Drain leaves. Meaning, reset to the point where
Toon Gemini Elf thinks it was summoned a turn or more ago.
If you negate a card with a condition like
Soul Exchange then you can proceed with your battle phase. (This includes
Toon Gemini Elf for consitent examples...)