You’ll need to save something to it before it shows back up. Share something, a photo from Photos for instance, then choose Save to Files and save it into a pre-existing* folder in the On my iThing folder at the bottom of the save dialog. It will then show up in Files.
*this is a bit of a caveat. You’ll need a pre-existing folder in there as you can’t share to the root. For instance I have folders created by Pixelmator and Transmit.
Thanks for the info guys - but WOW the Files app, while certainly pretty, is incredibly unintuitive - and so many clicks to do basic things. Documents by Readdle is far easier to use.
I hope that Apple will allow saving to root in "On My iPad" in the final release. I hate having to save Web images (that I don't want to save in the Photos app) into a folder for an unrelated app.
Any word on if this will be enabled when iOS 11 is released?