Steam Deck

Edit: This isn't about this specific game in particular! The point is that install folders are just disappearing when they shouldn't.

I have just installed a non-steam game right after a fresh re-image of SteamOS. Genshin Impact is the game in question. At first I added the installer .exe to Steam as a non-steam game and successfully installed it. The next step would be to add the launcher .exe as a non-steam game. But I couldn't find it in the 'Steam/steamapps/compatdata/[random numbers]/pfx/drive_c/Progam Files (x86)' folder like expected and just installed it again without thinking twice about it. This time I could find the launcher.exe and added it as a non-steam game.

Now I could launch the launcher.exe through Steam and installed Genshin Impact from there and chose the C:/Program Files (x86) as the install location (from a weird Windows looking directory chooser). The game downloads and installs successfully and I close the launcher. Now the next step of the guide I'm following tells me to switch back to Gaming Mode and launch the game. I do that and it immediately closes again. I go back into Desktop Mode to see what's up. Maybe it just can't launch in Gaming Mode, but in Desktop Mode it behaves the same and closes immediately. To investigate I navigate to the installation folder again and see that the launcher installation has completely disappeared but the game itself is still installed and after adding the GenshinImpact.exe as a non-steam game I'm able to launch the game without problems.

But my question is now, how do I prevent this from happening? Why does a folder just disappear? Again I'm on a freshly re-imaged SteamOS and this is the first thing I've done before setting anything else up.

Any help is much appreciated!

Notes: This is the guide I was following to install the game

As a side note: In the video the guy is just right clicking and selecting 'Add to Steam' in Desktop Mode when I do that it just opens the dialogue window to choose the file I want to add to Steam instead of adding it directly. Is this a setting or something?

It gets even weirder: Just now I wanted to rename the as a non-steam game added 'GenshinImpact.exe' and upon clicking into the text field all input fields on that interface just cleared. Of course I wanted to add the target again and what do I see? Nothing. The game just disappeared. What the hell is going on?