Long story short,
my cone nut came off while riding.
Can I put it back without dismantling my freehub?
And why I can't tighten my axle anymore?
Only way I can tighten axle is without wheel. As soon I put on wheel (with or without nut), my axle will just spin around. I have removed rear wheel multiple times and never had this issue before.
Could I have lost something during a ride when my wheel came off? Or maybe I don't know how to put nut back on?