Some servers don't have ZoneStats reporting turned on, so if you're playing on one of those servers none of your results will show up because the server simply doesn't report anything at the end of the match.
There's an option in the server set-up screen that allows you to turn reporting on or off, and I know on
Shiro, for example, they're turned off, so if that was the only server you played on your stats would never get logged at all.
Why are they off on
Shiro? (and all of the other
Banzai servers as far as I know) Back in the bad old BK pop-tart days, there were some players who were major-league stats-hogs, constantly trying to pump their own numbers, sometimes at the expense of their own team. Since no one else took the damned stats seriously, we just turned them off and the hogs stopped coming around.