At the very beginning, when she is showing a tutorial on how to catch Pokemon, she catches the bunnelby with a fletchling. None of these appear in the game later onn, so she has either released them, or stored them. Since "Pokemon trainers are supposed to raise their Pokemon with love and care" She probably won't have released those two, and it is obvios that tierno knows how to use storage boxes (he told us abut it in santalune), and so does cassius in camphrier town, so can Serena use it as well?
