This is a common concept used in Tokusatsu. But mostly made famous by the Heisei era of the Kamen Rider Franchise
It is a concept made up by fans of Kamen Rider to explain certain things that would not make sense in real life. But is necessary to keep the episode short.
Kamen Rider Decade Most times the main protagonist gets and stores cards from his Ride Booker which seems to have an infinite amount of cards. And Decade always seems to draw the card that suits the battle the most. For some reason at the end of every second episode the cards seem to have their own will and fly out of the Ride Booker in to the hands of Decade and show up re-powered. This can be explained by fans as Rider Physics. In episode 11 of Kamen Rider Decade the newly introduced Kamen Rider Diend (Who also has a pocket with infinite cards) steals the Ride Booker from Decade and nearing the end of that episode he does not seem to have it any more. Only to suddenly have it in his hand. Making it appear like he just pulled it out of his ass. Fans quickly attribute this to Rider Physics to explain this plot hole away and stop a pointless conversation.
Kamen Rider OOO An constant theme can be seen in Kamen Rider OOO where the main protagonist Eiji is constantly switching medals but its almost never shown what happens to the medals he switched the ones he uses with. Presumable he puts them in a pouch on his Rider Belt but every time his movements and the time he reacts in shows that he did in fact did not do so. So in fact it appears that the medals have disappeared in thin air.