Frank is still around in early November 1985, as he questioned Kevin after Kevin found Marie's corpse. I think Maggie was gone by this point. I think she left as soon as Marland's material began to air.
I wonder if Marland or someone at P&G had an issue with Mary Linda Rapleye, as Maggie was not only written out, but I don't even remember her being mentioned again, even though her entire family was still on the canvas and Marland's era was usually very good about history. I had no idea she even existed until I got the history book in 1996. It's a shame, because the character had some worth, and was a good contrast to Lyla and to Margo.