Yosha - I had this happen once on my SB3 13.5". I undocked the tablet and re-docked it. That seemed to make it re-appear in the device manager. Good luck!
This happened to me today after I updated my SB3. It's funny how the Microsoft Agent gives this long instruction set to attempt to solve the problem when your suggestion worked. Detached and reattached the screen and the 1660Ti showed up no problem. Thank goodness too because the Intel sucks when trying to run any half decent game with good settings and high frame rate.
Thanks!