Unity not picking up errors until after reopening

My unity game was running fine, but then after closing it down and reopening it, it crashed a few seconds into game play (I didn't change anything, just pressed play). After debugging it all I found that my game was getting caught in a infinite loop from the code. My question is how come unity didn't register/get caught in the infinite loop until after it was reopened? It seems to have to just skipped over the error.