Well. Strange had no idea Lambert could do that. Strange blinks, a little surprised as Lambert teleports away. He makes a mental note to bug the hell out of Lambert later before Strange looks at Rin and Herbert, giving each of them a glare that pretty much implies 'don't you DARE start anything or mention this to anyone.' Not even a second later, he starts to storm off to go find wherever the hell Lambert put that letter.

Because Lambert's right: he really does need to get rid of the thing, if only due to the fact that the 'sorry I'm leaving' part doesn't really apply anymore.