Is there any documented game by Benjamin Blumenfeld where he played Blumenfeld Gambit?
I am sorry I have no sources, but I have read somewhere (maybe in Yermolinsky's The Road to Chess Improvement - but apparently not) that no, there isn't any known game of Blumenfeld employing his eponym opening. The gambit is named such just because Alekhine, when annotating his famous Blumenfeld win against Tarrasch, wrote that "4...b5 is an idea by Blumenfeld".
