Another issue I discovered with my iPhone today, besides the problem of it not alerting to a new watchOS version, is that restoring an iPhone from a backup with iTunes requires a lot of temporary disk space, and if you don't have enough, the restore operation will partially fail, silently leaving the phone with some apps (and their data) missing.

If you notice, as I did today because most of my apps were missing, you can clear out disk space and re-run the restore.

The first time I encountered this kind of problem was a few months ago when restoring Anthony's phone. At the time I didn't know what caused the apps to go missing, and he was crushed to lose almost all his data.

At least now I know how to prevent it in the first place.