Answer
Most IFS-generated packages tied to a table/view include a Get_Id_Version_By_Keys-style method for exactly this purpose, though its visibility varies — sometimes it's exposed as a public method you can call directly, and sometimes it's private to that package. If the specific package you're working with doesn't expose this method publicly, you may need to write your own wrapper that queries for the OBJID by key — just be mindful of the security implications of exposing OBJID lookups more broadly than necessary, since OBJID is effectively an internal object identity value.