Do you ever just know? I was at an Irish Pub tonight and after a meal at the bar I ordered a Macallan 12yr. I ordered it neat. I took a sip and it stung me like a rattler. I asked the bartender for a side of rocks and dropped in a cube. It still stung me. At first I thought maybe I'd lost my Scotch whiskey "chops". But Macallan 12yr is aged in Sherry casks which imparts (among other things) a bouncy, rubbery mouthfeel which was virtually absent from what I was drinking. I told the bartender "Dude, this ain't Macallan". He assured me that it was indeed Macallan (surprise). I paid my bill which included the Scotch and chalked it up to experience.
Do you ever just know that what you are drinking isn't the real deal? What can really be done about it? How common is it do you think?