According to your screenshots, you have Krypton selected as the notification sound in the list, is that the sound you like and want to keep or did you just select it accidentally?
If you change to another sound and select Krypton again, does it still show up as 43?
When I go into sounds list, it automatically selects krypton, but its not the sound running. I have to cancel the list , if I tap “ok” I’m afraid that it will select krypton (which I hate… 
) as default notification sound , and then I’ll not be able to find back my current “43” sound…
Ok, understood. And you tried out every sound in that list and none of them is the one you had selected before, right?
As I said above, the 43 sound is running when the phone is ringing so the sound is in the phone, but not in the list… Android seems to hide some sounds from that list, is there a way (maybe via a pc connection?) To find these notification sounds in the phone’s system folders, and then copy/paste them in a “ringtone” folder and then be able to select them.from the “add new sound” menu ?
Yep you’re perfectly right!!
I had something similar with my FP3. I’m not sure how I resolved it but will see if there is old er post on that. Else check which apps you use for accessing files and using media.
See also
Ok, I searched for a wile but didn’t found other topic about this specific problem… I keep looking for it trying to read lots of posts…
Even on the internet, I only found a similar issue about samsung phones, solved buy downloading a third party app to get back original samsung ringtones… But I dont really want to install an app for that…
I’m using Cx file explorer to explore my phone’s files…
I takena look at that
The system notification sounds should be located at /product/media/audio/notifications. It’s 75 ogg files, with 2 duplicates (vega vs. Vega & arcturus vs. Arcturus). I exported them and uploaded to Google Drive:
https://drive.google.com/drive/folders/12yDGfOHDojtR6BOImvBGTtkO5WXffCTf?usp=sharing
Ok! I got it!
I can dl the whole thing on my pc , I’ll listen these sounds and tell you if I find back sounds I liked.
Thanks !! 
I checked the last three releases and the files in that folder haven’t changed 
Not sure what’s going on here…
I compared the list you sent to me, and it’s exacltly the same I can find in my phone… There isn’t any of sounds I had before…
I agree, its weird…
I feel stupid to not having get their name in mind…
I guess a total reset of the phone could solve the problem… Not sure I’m ready to restart all the setup of my phone for 3-4 notification sounds…
I cant find the path you told me above, to reach the folder where sounds are stored in the phone (even if I’m looking for hiden folders/files)
Not all file managers are able to get there. I use Total Commander (“File system root” folder):
Very weird indeed. I don’t think you’ll solve this with a factory reset, the sounds you can select as notification sounds are the ones in that folder. I just checked an old FPOS version from the beginning of the year and they are all the same.
When you say ringing, do you mean you hear that sound when you get a call?
If that’s the case we are looking in the wrong place…
I setted this sound as notification sound, so yes, the phone ring the “43” sound when I receive a notification
It think the list also loads files located at the user’s Notifications folder. (I haven’t actually tried that, but it definitely works for Alarms.)
It does, yes.
Just wanted to make sure we understand each other correctly, to me ringing means the phone’s ringing, we are probably all not native speakers here, so sometimes stuff gets lost in translation 
Yep, I’m french, so sometimes I’m not clear in what I’m trying to describe… Sorry for that!
But yes, I’m speacking about Notification sounds, not about phone calls 
I DL Total Commander and found the path you told me above, but no way to find the sound!
It’s crazy that the phone plays a sound that actually doesn’t exists in it! 