I watched it on TV, so I can't comment from experience.
However. At the time we had Trusty, Osulu, Slimane, Brewster and Wes on the pitch. It would have to be some seriously crass person to shout a racist comment at a one of several people of colour in Luton shirts. If said word could have been mis-heard, given that particular person of colour Luton player was also quite rotund for a professional sportsman, and said team were fortuitously in a leading position with a mere 2 of 8 extra minutes added on to play, it might be advantageous to mis-hear a certain word in order to kill off any momentum left in our largely exhausted 11 still on the pitch, pressing for a desperate equaliser, would it not?