Recovering a video that was deleted from a micro SD card after a factory reset
NOTE: I am not sure if this will work, this works if file is deleted or when sometimes files just dissapear(It has happened to me).

IMPORTANT: DO NOT USE YOUR SD CARD TO STORE ANYTHING NEW, IT CAN/MIGHT OVERWRITE YOUR DELETED/LOST FILE

Put it on your computer and use a specialised software for file recovery(try Recuva by Piriform, here: https://www.piriform.com/recuva). It will the SD card for any deleted/lost files it can find and you can recover them.