first, you might want to post your PID, so we can actually have a look at your stats.
second, it can take a while until that information is added here. We get our stats from EA, and we can only update what we receive. Moreover, kill streaks and death streaks, just like the favourite victiim stats, seem to be messed up a little on the EA side, IIRC.
third, 72/4 really doesn't necessarily mean your kill streak actually imrpoved through this. You could have had one death every 18 kills, and maybe your previous best kill streak was better than that already. Are you sure that somewhere along the line during that round, you actually surpassed your previous kill streak ?
My suggestion would be to wait until your next stats update here, maybe until tomorrow. If we get updated information from EA on your stats, they will be updated. And if we don't, that would mean that
a) you actually did not improve your previous best kill streak
b) you did, but EA failed to record it / send it to us.
Either way, there would be nothing we can do from here. Remember, we only display stats, we don't gather or manage them.