Quoting Dave Huang,

> My machine crashed today, but I was running X (in a pcvt virtual
> console), and couldn't figure out how to switch back to vt0 to look at
> the panic message. Is there any way to do it? :) Normally Ctrl-Alt-F1
> does it, but that doesn't seem to work when in ddb. I'm running the
> AcceleratedX server, if it makes any difference.

Unfortunately: no. X may have done all sorts of things to your video mode,
and the rest of the system has no knowledge about it, so it does not
know how to restore text mode. The VT switch in pcvt out of X works,
because X is signaled to switch, so it has the chance to save its
own state and restore the old one, something which it can do because
it has knowledge of the current state.

- Frank