I see it all the time with FOIA requests..... "sorry the data was lost or corrupt"
I actually wish they'd start making all cars with "black boxes" and have cameras mounted in various directions recording to a memory chip constantly. It would be trivial to add a microphone to the driver's door to record police encounters too. If even 50% of vehicles had this, it would pretty much make all traffic accident trials go a lot quicker as nobody would be able to lie about what happened.
As for me, I haven't been pulled over in years. But next time it happens, I plan on turning on the voice recorder on my iPhone and setting it in the door handle before the officer gets to my car. Not that I expect problems from the officer, but in this day and age it is better to have a recording and not need it, than to need a recording and not have it.