Its certainly possible. Some folks don't mind it, others can't even tell its there. Still, diacetyl should not be present in a properly made lager. And I believe that beer is a lager.
Lagers are cold fermented, meaning, the yeast used is "bottom fermenting" and the beer/yeast ferments at ~40-50*F. After fermentation, the beer temperature is then risen to 55-60*F for a diacetyl rest. This rest can last from 3 days to a week. During this time, the yeast consume the byproduct.
After the diacetyl rest, the lagering step begins. This is where the beer is slowly brought down to lagering temps, which range at 32-35*F. Lagering lasts from 4 weeks to whenever.
There. More Beer making trivia for ya. //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif