This motel was used by the B.G.A.T.F.B.C. (Bad Guys All Together For Book Club). The villains only entered their room to find two anonymous men in their room that claimed they were the I.J.L.S.A. (International Justice League of Super Acquaintances). These men then took off their trench coats to show they were Mermaid Man and Barnacle Boy.
A battle unleashed in the room until the villains were tied up in the Hairnet of Knowledge, and they revealed what the acronym was for.
It would be impossible for Mermaid Man, Barnacle Boy, and the other superheroes to enter the motel since only villains or the evil can enter the motel, hence the name. They may have snuck in or entered in another sleuthing manner. Besides, Mermaid Man and Barnacle Boy were hidden in trench coats in the conference room.