Remote Buddy depends on the iTunes Library XML file (*) that iTunes 
regularly generates based on its proprietary library file. Since the 
XML file is nothing but a copy of the library iTunes uses, that 
episode must also be in your iTunes library.

What you describe could f.ex. happen when you manually removed the 
episode's file from your harddrive, but didn't remove its 
corresponding entry from iTunes.

Best regards, 
Felix Schwarz

(*) That XML file is strictly read-only. Changes you make to it will 
be ignored and overwritten by iTunes.