Cheers Shane!
AUTOMOUNT + SCRUB (either of them or both) did the trick, now i have everything fine. Pool present and well, and no needless drive letters.
Automount + Scrub
To fix Windows no longer automatically assigning letters to external drives, try running the following command (first access the Run dialog, e.g. by using the key combination of Windows+R):
DISKPART AUTOMOUNT ENABLE
I don't know if that might also help with the pool vanishing.