I don't know about using meetings as a "cover" insomuch as the person is actively seeking dealers or buyers, but I do know that my exAH used to tell me all the time that he was going to an AA or NarAnon meeting, but then would disappear overnight. So odds are, he was not going at all, or if he was, he would go only long enough to "prove" that he had been there, pick up a can of Coke or a snack, & then leave.
Try to focus more on the overarching issue: trust & transparency in your relationship. If the issue SEEMS like "meetings", chances are it goes deeper, to whether or not your person is honest with you at all, and whether or not your gut is telling you not to believe him.