Looks like it was doing exactly what you asked it to do:
You are running old QMP and old firmware. QMP 3.09 cannot reconnect to a quadstick if it disconnects on USB. QMP 4+ can detect and reconnect as the quadstick changes USB modes.
When you reload the default.csv, or the prefs.csv (Save Preferences) to the flash drive, the quadstick will automatically reload them both in a few seconds. It does not do that for any other configuration file.