The sleep mask is one of many questions that spin about his head but at the same time, one of the reasons Donnie hasn't questioned too hard if this is really Leo or not. Who else would wear such a silly thing? Hanging onto that thread, brief as it is, Donnie can piece together enough and it makes him all the more glad he's there. Leo had missed him too, Leo had thought-

Oh.

Neutral as it is, the main point isn't lost on Donnie. He does a poor job at keeping it from his face but he's too tired to manage it. The thought that Leo had been convinced he was gone twists something deep in his gut, an all too familiar feeling that makes him queasy.