The Republic of Ireland international hit the ground inside the penalty following a challenge with Albion defender Craig Dawson and although Ben Foster saved Nikica Jelavic's penalty, Liam Rosenior reacted quickest to head in the rebound.
Some pundits have suggested that Long went down too easily, but the 27-year-old has been adamant that there was contact with Dawson.
"He clipped me. I didn't dive, he clipped my heel. He didn't mean to do it and I thought it was a soft penalty. I got up straight away and tried to play on, but the referee judged it to be a penalty," the Express & Star quotes the centre-forward as saying.
Long has scored four goals for Hull since his January switch from the Baggies.