When you’re disconnected from the Matrix while in VR without gracefully switching to AR first, you suffer a nasty shock as your sim module kicks out. This happens to hackers so often it has its own name: dumpshock.
I think having the connecting line cut on you would still qualify for dumpshock as you are snapped back to reality since we are presuming he has no other access to the matrix at that time.
you might or might not be correct
however i just want to point out that
you form your persona on the cyberdeck and you are not jumped into the device
in SR5 you don't actually "enter" the "node" you are trying to hack.
by the book you would suffer dumpshock if you were jumped into the device when the plug was pulled
or if the device is destroyed while you were jumped in
or if someone pull your cable between your datajack and your cyberdeck (or your control rig and your vehicle)
or if someone reboot, destroy or brick your cyberdeck (or whatever device you used to form your persona)