There's two aspects to this move:
1) Emergency Forward: The Rangers don't want to bring up -- and should not want to bring up -- a developing forward just to sit in the press box. Glass is not a developing player, he isn't going to be hurt by sitting around not practicing and he is exactly the guy you want in that situation (in a way) because you know he's not going to complain or drag down moral that he's not expected to play.
2) This will tell us a lot about Alain Vigneault: This is the kicker, though.