Damaged cylinder wall

[IDAHOSPUD]

Found a problem
Ive been doing the RB head mod to my ec300, just got the part back from RB-designs. I decided to put new rings in the bike as i had it torn down this far, might as well . . . . . .
Anyway, i remove the cylinder from the engine. I go to take the cir-clip off the side of the piston and its missing from one side, and the piston pin has been moving and gouging up the side of cylinder wall.
Glad i caught it before a catastrophic event deep into the Idaho wilderness. but this wont be cheap to fix either. Funny never felt like there was anything wrong with the motor, kind of down on power, but not terrible. so my questions are.

- How does one know if the cylinder can be fixed and replated?

- Is that the best way to go, if it is fixable?

- looked everywhere cannot find missing clip, could it have passed out without doing anything? missing from the factory?

Already talked to gofasters about a S3 cylinder, might be an option if fixing is not possible. more money then i wanted to spend.

Any advice would be great. thanks