In my current project I have
#include <DHT.h>
#include <DHT_U.h>
#include <Arduino.h>
#include <U8g2lib.h>
Yesterday I had these libraries installed; God was in His heaven and all was right with the world.
This morning I had to re-install them before I could get any work done.
Are the Arduino Fairies just having a Bad Hair Day and taking it out on me, or is there some reason for the dis-installation? If there is a reason, how do I avoid it? (Re-installing is just a PITA!)
Thanks
I just check my libs in the secret version of my IDE that I aint telling about and My faeries were good to me.
I also checked the not so secret location where I hide em and bejesus its still there too.
What you secret IDE version just so I can tell the fairies where to go again...and in case they get konfused where did you put them there libs. 
ballscrewbob:
What you secret IDE version just so I can tell the fairies where to go again...and in case they get konfused where did you put them there libs.
d:\Documents\Arduino\Libraries
and, surprise, surprise, they're still there!
When it says "workspace" is that a local physical drive or a shared location ?
Doesnt look like you have much in there so might be worth moving them out of documents to a different location to see if it still occurs and pointing to that in the preferences for checking.
Other thing would be what sort of security do you have as I have seen some stop files and wipe them if they were mistakenly placed in what I would term a vulnerable area.
Other than that this is more Perts field than mine.
ballscrewbob:
When it says "workspace" is that a local physical drive or a shared location ?
D:\ is the working area on my hard drive which I named 'Workdpace'.
ballscrewbob:
Doesnt look like you have much in there so might be worth moving them out of documents to a different location to see if it still occurs and pointing to that in the preferences for checking.
Something I read (always suspect :o ) led me to believe that Documents\Arduino\Libraries is where to put such files.
ballscrewbob:
Other thing would be what sort of security do you have as I have seen some stop files and wipe them if they were mistakenly placed in what I would term a vulnerable area.
I've never met a stop file. My internet security (if that is what you are referring to) is MS Defender.
vagulus:
and, surprise, surprise, they're still there!
The zip files of the libraries you downloaded are in that folder but the Arduino IDE doesn't use those zip files. You need to check the folder where the libraries are installed. That folder is the libraries subfolder of your sketchbook folder. The sketchbook folder location is defined in the Arduino IDE's File > Preferences > Sketchbook location. If you change the sketchbook location in your preferences then all the libraries you had installed to the previous location will no longer be recognized by the Arduino IDE. The won't be deleted as long as you don't delete them but the Arduino IDE only recognizes the libraries in the libraries subfolder of the current sketchbook folder.
The real libs are in the SKETCHES folder...DUHHH ME
OK drop them in the libraries folder that is inside your SKETCHES folder.
Why did I miss that ?
pert:
That folder is the libraries subfolder of your sketchbook folder. The sketchbook folder location is defined in the Arduino IDE's File > Preferences > Sketchbook location. If you change the sketchbook location in your preferences then all the libraries you had installed to the previous location will no longer be recognized by the Arduino IDE.
Uh HUH! 
That explains it.
I changed my Sketchbook Location to a projects folder from a folder which holds stuff I was doing from a textbooks and some tutorials. That change would have dislocated the libraries.
Thanks
