Conservation of Mass

In my new hobby of beer brewing, I would daresay I have had a string of successes.  Batch #7, though, not so much.  It turns out it is very important to mix the prebottling sugar around before bottling.  This is the sugar that will give the yeast a second round of fermenting in the bottle in order to give each bottle its own champagne-like carbonation.  Sloppily, I poured the sugar in and immediately bottled.  Turns out the first six bottles I opened were flat, like so:

I tried adding sugar to the bottles individually, but one week later they were only marginally improved - like so:

How about that lightning mcqueen cup in the background?

Now, just as I was wondering "Where did all the sugar go? I mean - it has to be in some of the bottles, right?" I open a series of bottle that are... over-carbonated:

Note the frothy beer still in the bottle as well!