I know this answer is not what you want, but sometimes stuff just happens and the file gets corrupted.

Will it ever happen again? It is quite possible that it will and it is just as likely that you will never figure out the sequence of events that caused it to happen. It is also possible that file becomes corrupted again and your current remedy does not work.

I had an experience in college where I was able to identify a bizarre cause for a programming problem.

It was a Friday and I had finished my code for a database system and only need to make the final runs on it before needing to submit at the end of the following week, so I decided I would take the weekend off and generate my stuff on Monday. I came in Monday and guess what, my code refused to run and was throwing an invalid record error. Through shear luck I found if I added a line to seek the first record in the DB prior to actually running my main code it would work. I asked the operators (yes this was the days of mainframes) if they knew of any issues with the drive systems and got laughed at. A week later they told me that their boss wanted to talk to me. It turned out that a disk controller had failed and he wanted to know why I suspected that there was a hardware problem. I explained the scenario to him and was dismissed again as a crazy kid. I decided to go back to my program and remove the dummy code that I placed in it to make it work and it did just as it did before the issue arose. Would that same condition ever come up again, not very likely.

So sometimes, sh*xyz*t just happens, and you just have to accept that.