Did you have your scorer calling out the value for every shot?
Per the rules, that is the correct procedure - see rule 14.3.1(c).  If the scorer is calling out your shots, and you're paying attention to what they're saying... then its usually pretty easy to catch a missed shot right away.  Yes, its annoying to have to call out 'DID YOU GET THAT?' but its a lot less annoying than getting to the end of the string and having to argue about whether you have rounds remaining.  
Assuming you lose the argument - and most of the time, you will... - then you have to get back down and fire the missing rounds, and at that point your head ain't in the right place, so inevitably, you're going to drop an X or a point.  One of those Murphy's Law type of things 

  The *only* time I've won those arguments was when I had a plot sheet handy and we could figure out exactly where they missed a shot.  Spent cases in a loading block or ammo box never seems to convince 'em 
Also note... if you tell the scorer to *not* call out your shot values, you forfeit any right to challenge the recorded score.
I know it can be hard to hear the shot values at times - between the gun fire and plugs/muffs, etc. but it behooves you to make *sure* your scorer is keeping up.  *Especially* if you shoot fast.
YMMV.  This is stuff I've learned the hard way.  It's not always the scorer's fault - sometimes they blink or look away at the wrong moment, and miss a quick target pull.  Sometimes someone comes up to them asking them questions - including the range officer - when they're *trying* to do their job.  To me, it's kind of like cross-fires... sooner or later, when you score, you're going to miss a shot somewhere.  
Back when I started out and the guy next to me missed a shot during a 500yd prone stage while scoring for a well known and prominent HM shooter... the competitor (kind of old and cranky anyways) fixed him with a glare and told him that if *he* had been scoring for a HM shooting all 10s and Xs, and had missed a shot while scoring... he'd probably take the leap of faith that he missed an X in the middle somewhere and quietly mark it as such.  While there is a certain logic to that... bullying the scorer (a beginner at his second match) because you don't keep a plot sheet and didn't pay attention to the scores being called out is poor form, in my opinion.
YMMV,
Monte