The 23-year-old was given a yellow card by referee John Beaton following a first-half collision with former Tynecastle team-mate Jason Holt.
But television replays clearly show the Rangers midfielder making contact with Walker’s legs.
Walker has already served a two-match ban this season after Beaton awarded him a penalty during the Jambos’ opening day clash with Celtic. The player was later found guilty of simulation by the SFA.
Hearts were successful earlier this season when they challenged a yellow card handed to striker Tony Watt for simulation in a 3-1 win over Hamilton in September.