Then it still wasn't finished carbing when you opened it- no matter how long that was. It might have taken months longer, but it would still eventually carb, as long as you had any yeast at all.
Remember, the yeast don't dictate how much CO2 is produced- only how quickly they eat the sugar. The amount of sugar you put in for priming, as long as you're fermenting dry, will always produce a predictable amount of CO2 volume.
If you want, you can always mix up a little fresh yeast with your priming sugar for your bottling bucket. It'll of course give you back some yeast haze for a while, but you'll get the benefits of aging AND fast carbonation at the cost of a small amount of shortlived haze.
The other option is to forget naturally carbing and force-carb in a keg before bottling... that's what I'm planning for my wedding favor batch.