Ah, records being pulled from under your feet right when they're surely yours.
A couple of my experiences from a few months back:
In Sonic Rush score runs, it's in your best interest to max out the trick ranking, then purposely die and then play through the level. On Night Carnival 1, I believe it was, I had finally broken 300 rings on a score run, getting maximum rings from both random containers, and finishing the level with style. It was going to be enough for a new high score. Moments after, I discover on this particular run (had been doing quite a few) I had forgotten to max out the tricks beforehand XD. This means my score had failed, and I haven't had good enough luck for both random containers to be maximum values on a score run ever since...
Also relating to Sonic Rush, on the Altitude Limit boss, in one of my runs, the boss attack set truly couldn't have been faster, allowing me the chance for a (near) perfect time. Then on his last rather simple attack, I got hit...twice XD, causing me to lose several seconds, and ruining my claim to such a record.
It always sucks when stuff like this happens, but if everything went smoothly and according to planned all the time, life would be pretty boring.