Sticky play (just to make sure)

[OverAndBack]

This happened this afternoon, opening kickoff of a junior high game:

K1 kicks off. R1 fields the ball at his own 5 and starts running. K2 grabs R1's face mask on the tackle. R1 fumbles. K3 picks it up and runs into the end zone.

Our referee gave R the ball and marked off the face mask penalty, first down and away we go. No one complained.

Was that right?

And now that I sit here and think about it, can K even advance a fumble like that?

Sorry to sound dumb - I've done four games in five days and my legs and brain are fried.