On March 18, 2014 Lehner started the game, but Lawson came in net at the beginning of the 3rd period. He then had to leave the game after 11:52 minutes due to injury.
I don't have any information on Lawson's mask. (Scott mentioned in a comment below that he thought he remembered Lawson saying the angel was in honor of his wife or family, and that does sound slightly familiar. I might need to look up that Montreal mask and see if I can find more.)
I looked back at Lawson's 2011-12 Montreal mask, and a reader said "The depictions are of his family, and the top illustration is of him being the Guardian." It could be a similar theme with this mask, but I can't say for sure.