Here is a link to a good article on White Lab's site regarding diacetyl - http://www.whitelabs.com/files/Diacetyl_Time_Line.pdf
Thanks for the info! I think the section below is what happened to me. I don't normally do any type of diacetyl rest because I have have never fallen victim to it. Normally I keep batches in the primary for longer which gives it time to clean up. I pulled this one off the yeast too soon...
"Usually the diacetyl rest is begun when the beer is 2 to 5 specific gravity points away from the target terminal gravity. The temperature is then lowered to conditioning temperature following diacetyl reduction. For ale production, the fermentation temperature is usually 65-70F, so temperature modification is not necessary. But the fermentation should still be "rested" at this temperature for two days to ensure proper diacetyl reduction. Many brewers make the mistake to quickly crash the fermentation temperature following
terminal gravity. Why not? The beer is done, people are thirsty, and there is no taste of diacetyl in the beer. Even though the diacetyl can't be tasted, however, the beer may contain high levels of the precursor,
acetolactate, which can be converted to diacetyl. Once the yeast is removed, there is no way to get rid of