1997 Polaris 700 RMK Engine Issue

I have a 1997 Polaris 700 RMK that has been running pretty good for the most part. She is one of my back up sleds and has 3000 miles on the engine. I took her for a ride on sunday and got perhaps a quarter mile from the snowpark running perhaps 6000 rpm's on the tac and suddenly I hear a pop and the engine over revs and she stops in her tracks. I found out that the primary clutch came off of the crank and the bolt that holds the PC to the crank was not sheared off thank goodness. When I placed the primary clutch back on and tried threading the mounting bolt onto the crank the crank turned not allowing me to tighten the bolt. The engine did not seize. Is there cause for concern? The question I have is perhaps the crank snapped or maybe something else? Any answers would help before I have to tear into the engine.

yes I did use a ratchet strap to prevent the primary from spinning. Its when I was threading the bolt into crank that the crank was spinning.