Card Effects V1.1 Attachments indicates, "For example, if an attachment had the requirement "Attach to a Servitor character," and if the Servitor character...loses the Servitor subtype, the attachment would still remain."
Is that surprising. Is there a similar example. It was when you did. And the condition need only have been met then. It's not like the interaction is over. M.U.Science Building (which by the way is rumored to be included in Secrets of Arkham as a Zoog card) is dishing out subtypes while University Umbrella (also rumored) MU attachment (attach to an esteemed author) gets a pass.