Distance penalty for illegal kicking or batting the ball was changed last year from 15 to 10 yards.
It is not loss of down.
Loose ball play -- basic spot is the previous spot. If the foul occurred behind the basic spot then distance penalty is from the spot of the foul and replay the down. Or, refuse the penalty and accept the result of the play (treat the ball being loose after the illegal kick as just part of a fumble). Was team A the team in possession at the end of the down? Was the end result of the play beyond the line to gain.
Lots we don't know from the original post.