The Northern Ireland international was furious after the incident which occurred on Saturday as the Baggies were beaten 3-1 away at Reading in the FA Cup fifth round.
Police have arrested an individual as part of their investigation into the incident in which a coin was thrown at West Brom midfielder Chris Brunt.
The Northern Ireland international was hit by a coin thrown from among the visiting supporters as Tony Pulis' side was beaten 3-1 away to Reading in the FA Cup fifth round on Saturday.
Brunt, who had gone to hand his shirt to a child in the crowd, said he was "disgusted" and "ashamed" by the incident and West Brom assured it would issue a lifetime ban to the culprit.