It’s a dock glitch. It’s still docked to your ship but 2-3k away, and it will fly with you. Use a different ship to get to it, and get in the cockpit and fly it back to your cv
Open your in game registry and find the SV and set it as a waypoint.
Open the command console window and enter this command without the quotes,
“undock 11679550”
Hopefully the SV undocked and you can now find it by the waypoint.
Now, it may not work the first try. Alternate between trying the command at the CV and trying it at the SV waypoint (while not moving the CV).
When it does undock it may be at the waypoint 1.2 miles away, or it may suddenly appear back at the CV.
It may also be at the waypoint but once you get within render range it may update and suddenly be back where the CV was.
Hey, I don’t know if you tried the above yet, but since the ship was still under the ground I moved it up to the surface again.
It’s on the Giaurein planet by 14495, -2764.