In the case of B2 bunting and the ball going high into the air to F2, what happens to R1 if he does not return to first base?

In this scenario, if R1 does not return to first base after B2 bunts and the ball is caught by F2 (the catcher), R1 is considered to have abandoned his occupation of first base. When a player leaves their base and does not return while the ball is in play, they can be declared out if a force play situation is enforced.

Since F2 caught the ball, this creates a force play at first base. R1 must have retreated to first base before the catch is made. Failing to do so means that he is at risk of being called out due to not tagging up properly after the catch. The only scenario where R1 would be safe at first is if he had legally occupied that base without leaving it. By not returning, he forfeits that right, making him subject to being called out when the defense appeals or tags the base.