How do I delete a real media file from the ipad mini

I clicked on a video with a ".rm" extension, and the pop up window came up with the file name and a link to "open in usb disk". I clicked on the link and was taken to that app, but I could not find the file. Is the .rm file on the ipad? I can't see it in the usb disk app. If it is on the ipad, I would like to delete it.