The Baggies looked short of confidence in a first half that was low on entertainment and saw them fall behind in the 28th minute when Jake Livermore, on loan at Hull from Tottenham, finished off a counter-attack.
But after leaving the field to the sound of boos from their own fans at half-time, Albion improved in the second half, with substitutes Saido Berahino, Vydra and Zoltan Gera - who teed up the equaliser - giving them fresh impetus.
"The dressing room is devastated that we didn't hold on," Bruce said.
"It (the goal) is the only time really in the game that Shane Long (who fed the ball to Gera) has got down the side of us.
"It feels as if we have been beaten.
"I think a big turning point in the game was the chance for Elmohamady, where Foster makes the double save.
"It could have been a different scenario, but there you have it - that is where we find ourselves, and we will move on."