Thrown ball kicked by runner

[QuinnVT]

I couldn't find how to handle this in the case book for HS, so I thought I'd ask.

Play at the plate: F3 thows to F3 who drops ball. R1 slides into home and happens to kick/move the ball up the 1B line during his slide. Since I didn't see any intention in the act, we just kept playing. Coach wanted runner returned to 3rd.
What's the call here and just for my learning does it make a difference if the ball was hit after the R slide across the plate?