Wrong number reported for foul

[lukealex]

I once reported the wrong number for a personal foul, I believe I reported 20 instead of 30. I noticed the fault after the ball was live again, then at the next dead ball I changed the number with the scorekeeper. This happened in the beginning of the game, so my question is:

Was I correct in how I handled the situation, or should I have done something different?

Also, what if this happened late in the game (doesn't have to be late in the game) and the player that committed the foul had 4 fouls and would be disqualified from the game with his 5th foul, but the wrong number was reported, allowing him to stay in the game. The fault wasn't noticed until the ball was live again with the player that should be disqualified still playing. What should be done in that situation given many different scenerios that could happen by anyone (the disqualified player included); someone scores, a foul, etc.