At 15:22 of the second period in the Blues/Flyers game, Philadelphia requested a Coach's Challenge to review whether St. Louis was off-side before Paul Stastny's goal.
After reviewing all available replays and consulting with the Linesman, NHL Hockey Operations staff determined that the review was not conclusive in determining whether St. Louis was off-side prior to the goal. According to Rule 78.7, "If a review is not conclusive and/or there is any doubt whatsoever as to whether the call on the ice was correct, the On-Ice Official(s) will be instructed to confirm their original call."
Therefore the original call stands - good goal St. Louis Blues.
Since the Coach's Challenge did not result in the original call being overturned, the Philadelphia Flyers forfeit their time-out.