Post season tournament rules? No. A cannot re-enter for C. A and B are 'paired'. If no eligible subs are available (all are already paired), the opposing manager may select from players not currently in the lineup for who will sub for C. Now that selected player and C are paired. Selected player un-paired from his original partner.
I do not. However the nature of the game is that the call is made by the umpire and it is not the players place to correct him when the wrong call is made. If a player comes up and says "Hold on, I dropped the ball, you didn't see it because of ..., but I dropped it and didn't have a good catch", how long does that player keep his job? How does this discussion change when it's Little League where the player is not paid to win? I know coaches that would penalize the player w/ less playing time if he gave away outs.