What should have happened here?

[aharner]

This was in a high school game in Illinois. On fourth down, the opposition was punting, but there was a fumble because the punter has butter fingers. The punter recovered and tried to run ahead. He was tackled out of bounds, and the play is blown dead.

One of the home team's players committed a late hit out-of-bounds after the whistle.

However, the opposition's illegal motion penalty was waved off and the opposition was awarded possession and got an additional 15 yards and a first down.

Correct me if I am wrong, but the home team should have received possession and lost 15 yards from the spot, right? Because the play was blown dead, there should have been a turnover.