Not enough research.
7.12 Unless two are out, the status of a following runner is not affected by a preceding runner’s failure to touch or retouch a base.
The BR did not "pass" R2. R2 crossed the plate (without touching it, I know), so he is assumed to have touched the plate until such time as an appeal is made.Once he 'crossed" the plate, he was no longer a runner.
These are replies from this post, and they got my brain thinking about an entirely plausible (and probably encountered) situation:
R1, less than 2 outs. Batter hits a HR. While rounding the ba