Very weird behaviour on my Samsung Galaxy J3 (2016) phone

[PowerPC603]

Today I've lost most of my settings suddenly.
I was at work and at the end of my shift, I looked at my phone and it asked for the PIN-code for my SIM-card as if the phone had been rebooted.
After entering the PIN code, I noticed one icon missing on the home screen: Netflix was gone and wasn't anywhere to be found, not even in the installed apps list.

Also, most of my apps had lost their settings.
My online banking app lost it's data and I needed to register again (it lost the data about my creditcard and account data).
Also the MyProximus app lost it's data. After starting the app, it asked for confirming some legal stuff and when that was done, it only displayed my own phone's data about 4G usage and total time I called while I'm actually the administrator of our internet connection and I should see alot more like my wife and son's data and home-internet as well. I had to re-enter the account details to get all that data back.

Highscores in some cardgames have been reset as well, as if they had been installed freshly.
My camera app gave a message it will store photo's on the SD-card instead of internal memory. So that app was reset as well.
Previously I deactivated notifications for alot of apps as I cannot be bothered by any app that needs some update or whatever, those notifications were active again.
And suddenly my phone started updating 33 apps (I deactivated automatic updating previously to avoid my phone's memory being filled with updates, this was active again).
Also my alarm schedules were gone, as well as all my notes.
The gallery was also mixed up (was set to display by time instead of album).

It looked as if all settings were reset somehow.
But it still had my gmail account, email settings were still fine, all appointments in the S Planner app were still there and facebook also had my account data.
Also the password to my wifi network at home was still on my phone as it auto-connected to the wifi when I got home without asking for the password.
Also the background picture was still there, as well as date and time was still correct.
To my knowledge, resetting settings wouldn't uninstall netflix and would probably reset all settings, not just a few select ones. This would also probably not affect highscores in games and account-data on every app.
Doing a factory reset would have wiped everything including facebook app, games, MyProximus and online banking app but those were still there so it can't be that as well.

It looks as if somehow a settings-reset has been done but wasn't completely finished (80% or so).
What could have happened here?
I suspect a collegue messing with my phone but I'm not certain.

Or did my phone do something weird somehow and reset 80% of all settings on it?

 

[Tim1954]

Sounds like a serious bug for sure! Are you sure nobody touched the device?
Have you had a software update or do a cache partition wipe recently?

 

[PowerPC603]

I'm not sure, I didn't see anyone touching my phone.
But I'm certain someone accessed my bag at work because I always put it in a certain position with the handle (or whatever you call the long strip you put over your shoulder to carry the bag) in an S-shape on top of the bag.

And it was definately in another position at some point during the day but I didn't think further at that point to check everything. I did check my wallet though because we were going to eat something and nothing was missing in there.
The bag was located on a table in a maintenance room which is normally locked (operation personel normally cannot enter that room). And it was on a very quiet day, only a handful of people where in that building with only 1 other maintenance person besides me. But he claims he didn't open my bag.

I doubt it's a bug, because of the abnormal position of the bag and it's handle.
Someone opened the bag, I'm certain of that.

I'm just asking this if there is a way this could be a spontaneous action of the phone itself somehow or if any reset function could do such things (clear some of the settings but not all and uninstall only 1 app instead of everything like during a factory reset).

I've noticed about a month ago that my google searchbar on the homescreen was gone as well but nothing else was affected. I thought my wife or daughter may had something to do with that.

 

[PowerPC603]

My collegues at work claim this behaviour might be a result of an Android update.
If this would be true, then Android would not be a good OS to use because it would be unreliable to store any data on your phone.
And they claim it's also my fault for not taking backups to Google Drive.
That might be true but a phone just deleting data because of an update or whatever is also wrong.
There is no way some highscores in a cardgame for example could be responsible for failing an OS update, for which the highscores would have to be deleted first.
Or some online banking data, or some notes.

And if the update is known to delete data, the phone should have asked me before running that update and deleting 80% of my stuff.

Could they be true, that this might be because of some update?
But when I look at my phone, the OS is still Android 5.1.1 while there are newer versions available.
So there was no update that could have caused this.