Busted

[DieselMonk]

2g? "g" as an "grand"
"k" and an thousand
those mean all the same thing. k and g.
2g = 2k = 2000

 

[Ductape]

Looks like a thin ring of rust just beyond the groove for the snap ring. I would smooth that out with some fine paper or emery cloth, just so it doesn't scratch your seals when you put it back together. Like everyone else says, order a new snap ring, put it together and run it. I'd chalk it popping out to somewhat of a fluke. Apparently that snap ring just wasn't quite doing its job, The groove looks clean, but I'd take a pick and double check that there is no crud in it.