I attached two screenshots of Lightroom Web. One from before I signed in to the desktop app, and one from after. Lightroom Web is empty.
Then there is something must have happened on the device on which you using Lightroom mobile, because once you add images to Lightroom Mobile from the Gallery it will sync to the Desktop Or Lightroom Web for more editing.
The iPad App did successfully send the images to the web. They weren't on the desktop because I wasn't logged in to the app.
When I logged in to the desktop app, that empty collection replaced the collection with photos in it. The iPad app isn't a mysterious boogeyman, as it was the last device to go empty.