As I had had problems with the haunts in the Foul Misgivings scenario, on my next group I remembered to keep the ally Aldern Foxglove when I found him in an earlier adventure. So now I play Foul Misgivings with Seoni at the Academy holding the Aldern Foxglove ally card in her hand, while Seelah at the Prison encounters The Skinsaw Man; and suddenly the screen switches to Seoni, Aldern Foxglove disappears from her hand, and is replaced by the Stalker Mask, without me having done anything that could possibly cause that.
Did I overlook some rule here, or is this a bug? Not that the Stalker Mask is a bad item, but it felt weird for it to suddenly appear and Aldern to disappear. Furthermore I can't see the Aldern Foxglove ally card in the Vault / Gallery, and have no idea how to re-acquire him. Any ideas on that?