Anelka was celebrating one of two goals he scored at Upton Park on December 28 when he made the gesture which is considered to be anti-Semitic.
The 34-year-old has since been charged by the FA over the gesture which is deemed to have been insulting and includes a reference to ethnic origin, race, religion or belief.
"If he gets a ban it will be a shame for us because in recent weeks he has come into form," Reid told Sky Sports News Radio.
"In the game in question against West Ham away he looked back to somewhere near his best. He got two goals on the day and even last night he looked a threat all night so if we're going to lose him now it will be a huge disappointment for all of us."
A three-man independent regulatory commission will now be appointed to deal with the case - either to decide on the sanction if Anelka admits the charge, or to hold a disciplinary hearing if he denies it.
Reid said the matter has not been a topic of conversation in the West Brom dressing room, insisting the only person that is capable of clarifying the meaning behind the gesture is Anelka himself.
"It hasn't (been discussed in the dressing room) to be honest because it's a gesture that has been seen in France," Reid said. "It's not a gesture that too many of us have been familiar with over in England.
"We've read little bits and pieces about it since but it's something you're going to have ask Nicolas about. It's not something we know a great deal about and something obviously he is going to have to explain for himself.
"It's out of our hands," Reid added. "We'll have to just wait and see now what comes of it."