When I got my Samsung Galaxy S5, I installed Hangouts (set to use with SMS) and disabled Samsung's pre-installed Messages app. But when I went into the Ultra Power Saver Mode, I discovered that Hangouts is not supported in that mode. 
Well, naturally, I need to be able to receive texts in Ultra Power Saver Mode, so I re-enabled the Messages app, and it works fine in non-power saving mode.
However, even after a reboot, when I enter UPSM, it still does not show Messages, nor does it appear in the list of available apps. It's my understanding that Messages should have been permanently displayed on the UPSM screen (i.e. I shouldn't have even been able to remove it), and so I assume the only reason it isn't there is because it was disabled when I first launched UPSM. (There was a glitchy moment where I tried to add Clock to the top right spot, and it did, but it called it "Messages" even though it launched the clock... again, seeming to indicate Messages should have been in that spot.)
Does anyone know if there is a way to reset UPSM to the default settings? I wondered if I could find UPSM as an app in the Application manager, perhaps I could clear the cache or data to wipe the settings... but I don't see it there (or I'm not sure what it's called).

Well, naturally, I need to be able to receive texts in Ultra Power Saver Mode, so I re-enabled the Messages app, and it works fine in non-power saving mode.
However, even after a reboot, when I enter UPSM, it still does not show Messages, nor does it appear in the list of available apps. It's my understanding that Messages should have been permanently displayed on the UPSM screen (i.e. I shouldn't have even been able to remove it), and so I assume the only reason it isn't there is because it was disabled when I first launched UPSM. (There was a glitchy moment where I tried to add Clock to the top right spot, and it did, but it called it "Messages" even though it launched the clock... again, seeming to indicate Messages should have been in that spot.)
Does anyone know if there is a way to reset UPSM to the default settings? I wondered if I could find UPSM as an app in the Application manager, perhaps I could clear the cache or data to wipe the settings... but I don't see it there (or I'm not sure what it's called).