RateTheRef

I watched the last few minutes of Larne v Crusaders on BBC i player. Crusaders were pushing for an equaliser and Larne had everybody back to defend a corner. They cleared the corner with a hoof upfield that went out of play about ten yards inside the opposing half. A crusaders player quickly took the throw in to the Goalkeeper who returned the ball to the other end only for the ref to blow his whistle because they hadn't realised a susbstitution was taking place on the opposite side of the pitch. However, instead of restarting with the throw the referee restarted play with a drop ball at the point where the keeper had kicked it. I'm not a referee but would like advice on whether he got this wrong.