Obstruction?

[Gre144]

R2 is on Second. The batter runner hits a grounder to right field. R2 is obstructed by F6 but mistakenly thinks he is out and runs towards the dug out. In the meantime the batter runner scores to home for an inside the park homerun.

How do you handle this situation since the batter runner passed the preceding runner R2. (Do you send R2 to third and the batter-runner back to second since it would be illegal for the batter-runner to score since he passed the preceding runner.)