ATEC's Credit a Hit #6 provides some guidance on ordinary effort in this case.
6. on a fair line drive hit to the outfield which drops to the ground, where the outfielder is attempting the catch on the run, not in a set position; or any fair fly bail hit to the outfield which drops to the ground, where the outfielder either had to cover a considerable distance or make the catch while running at a high rate of speed (credit a hit even if the ball is touched),
ATEC's Errors has one regarding collisions, but is only applicable if one player is making the catch before they collide.
x - If two fielders are running to field a fly ball, one catches it and the second one hits her and causes her to drop it, credit the error to the player who collided with the player who initially caught the ball.
Based on the info given, I'd score it a HR. Inside the park HR's in MLB are usually the result of a collision, misjudging the ball or weird bounce.