I remember hearing somewhere that he turned some of these jingles into real songs after word got back from some Midwestern radio stations that listeners were actually calling the stations requesting the commercials as if they were regular radio hits!
In the ad business, if the music is contracted out, the contractor naturally retains the rights. But, if the music is written by an employee of the ad agency, the rights are presumed to belong to the client. The client, after all, paid for it and the writer was acting as the client's agent.
Under the circumstances, it's evident that Fries sensed what he had.