If B4 swings and misses at a bounced pitch and enters the dugout, what happens to R3's run?

In this scenario, the key point is about the circumstances under which the run can count if a batter misses a bounced pitch. When B4 swings and misses at a pitch that has bounced, the ball is still in play unless it is determined to be a dead ball (due to specific circumstances like hitting the batter or an illegal pitch). However, once B4 enters the dugout, they are considered to be leaving the field of play, which has implications for R3's ability to score.

For R3's run to count, B4 must remain in play until the appropriate play concludes or an out occurs based on the rules governing batting and base running. Entering the dugout signifies that B4 is no longer a participant in the play, which affects the status of any runners advancing. In this case, R3 cannot score because the play is effectively concluded with B4 leaving. Thus, R3's run does not count, and he must return to third base.

It's important to understand that the action of B4 entering the dugout means that they are out of the play, which forms the basis for R3 not being able to complete their run to home plate.