I tried deleting the cache, etc., to get the reading list back but it wasn't until A VERY SIMPLE THING worked---scroll with two fingers up/down the space under the reading list icon and see the "All/Unread" tabs. Click on "all" and presto! they had been
"read" at one time or other, and reappeared; or, I guess, click "Unread" if they are unread to make the unread reappear. I have no idea how they disappeared (probably by my cat) but that's how it worked for me. BTW, I was not smart enough to figure this out myself. This fix was entirely due to a helpful person at the Genius Bar
in Marlton, NJ.
If this still doesn't work please also note that he showed me that my reading list was in my iPhone cloud
under Settings> iCloud, etc.