And no, it isn't that the filter's pulling out the alcohol... I poured the stuff back in the bottle it came from, and there just wasn't any visible product loss. To make a serious impact in taste to 80 proof liquor based on alcohol level, there would have had to have been a VERY obvious impact on the overall fluid level, and there wasn't.
Anyway, now I'm SERIOUSLY excited about the real experiment - trying the same thing with Early Times, the world's crappiest bourbon. I'll keep you posted. =)