Yeah, you'll want that back together.
That happened on a buddy's CB550 once. We were in a hurry to get it back together after a total rebuild prior to a road trip, so we pulled the oil pan and reassembled the kickstarter from underneath. He rode it out of the shop later that day on a 2300 mile trip! It held up fine for the last three years and he only kick started it since the battery was too small for the starter.
I'm not sure why it sprung apart, but it might have been a circlip issue like 754 said. I also seem to remember thinking he initially assembled it wrong since I remember there being a "bad" way and a "good" way to assemble it when I put it back together for him. Someone else might chime in with better instructions on reassembling it the correct way.
Good luck!
Camelman