Actually...it was late and I probably got it wrong.
Back in Jurassic times (my day), the bottom end of a motor had oil in it to lube the crank, so if fuel mixed with that oil, it needed to be changed.
Now bottom ends are, basically, dry, and only the clutch/trans are in an oil bath.
Although...I'm not familiar enough with Fantics to know if your intake is in the cylinder (and "wet" bottom end) or the crankcase ("dry" bottom end).
HOWEVER....if a carb float were to stick on a bike with crankcase induction, and the bottom were to fill with fuel, it would definitely need to be drained, and I don't know of such a bike with a drain plug for the lower end, so I wouldn't know what advice to give.
Short version: I would say that if there was definitely fuel in your airbox, it is probably in your bottom end, too, and it will not be good for the bike to run it that way.
As for draining the lower end, somebody who knows more about the make/model of your bike will have to step in.