Video assistant referees have been asked to be more proactive in challenging officials following a series of controversial decisions.
Premier League refereeing chief Howard Webb said VAR should have intervened.
"We are asking VARs to have a look and if they don't like the decision, ask the referee what they saw," said Webb.
With the game at 1-1 in first-half stoppage time, on-field referee Anthony Taylor awarded a spot-kick when Hwang challenged Schar for the ball in the Wolves area, but the Newcastle man appeared to kick the turf and looked to already be on his way down before any contact.