Update: so I opened one of the bottles I had submitted (bottled extra), and I do in fact get a very strong butter aroma. But the same exact beer from the keg, I am not getting any of that. What gives?
Hmm! Well! This is indeed interesting. How did you bottle? Did you use priming sugar, or did you bottle from the keg? Yeast eats diacetyl. If you have a little yeast in the keg, but none in the bottles, that could explain the difference. Could also be a temperature differential thing? Are the bottles at cellar temperature, or room temperature, or are they refrigerated cold? In any case, warming up diacetyl should help the yeast eat it eventually with age. But, if the yeast is gone and/or dead, the diacetyl could be locked in for a very long time or forever.
Hmm.