There is a problem with the Build UI that resulted in me thinking I lost the app I just wrote. So I wrote the app again and appeared to lose it again. And once again. Only to later find I had 3 copies of the app saved.
When writing a new app and saving it then selecting an old app to examine, the name of the new app did not appear under 'My apps". So I thought the new app was lost. But when I later used the ‘type to find’ window and put in the first few characters of the missing apps name, the list of all my apps was updated and included the three copies I wrote.
This failure to update the list of apps when a new app is created, made it appear that the new app was lost even though I saved it.