Re: What happened?
I'm assuming you have a 2-stroke?
If so?, the first thing I would check is the small gear under the large cover on the right side... Remove the cover & inspect the gear while rolling the bike back & forth.
You're looking to see if the gear is actually turning the crankshaft that it's bolted to.
Next I would do the same check on the small sprocket on the other side of the engine.
Report back what you find.