Sorry but unless you can supply a replay that is complete there isn't anything you can do but take this as a reminder that you must always check your replay before submission
I had the same trouble a couple month back, but fortunately for me it faded out going over the line and my lap time was still visible to see, but if it fades out before the line and goes off then that is a bummer.
It is just one of the many quirks of the game. It has happened to lots of people, like Mike said it is always good to check your replay to make sure you can see the time at the end. It is also good to check anyways in case you pushed the boundaries too hard.
Sorry for the black flag but I had no option. As I mentioned to RACECAR use this as a prompt to make sure you always check your replay before submission. The randomness of the inconsistencies in saves is such that you can never assume them to be OK
