Runner misses base
 

Having a brain fart moment.....can't recall the rule.

I ump asa (SP)...but it doesn't likely matter insofar as the ruling.

BR hits ball out of park....HR. R1 (who is on 1B) misses home plate while high-fiving teammates. BR...right behind him....touches.

Can R1 "re-touch", legally?

I hope I asked this, correctly.

Once a succeeding runner has touched home plate, no, they can not return to touch a missed base, including home plate.

More accurately, he can go touch whatever he wants ... but it means nothing and would still be out on appeal if the defense appealed the miss. At this point in your scenario, though, you have nothing.