The forward, 23, was sent off during his side's 3-1 defeat on Saturday after accidentally kicking goalkeeper Sam Johnson in the face.
The unsuccessful appeal means that Forrester will now miss Doncaster's next three matches.
"We are really surprised and really disappointed about this," manager Paul Dickov is quoted as saying by Sky Sports News.
"We felt we had a very, very good case put forward and we took a lot of advice from a lot of people in the game, including people within the referees, and to get knocked back was really disappointing."
Doncaster return to action on Saturday when they travel to Colchester United in League One.