that one you saw is the only one left
they only built two, and one of them crashed after getting nicked in flight by an escorting starfighter.
the valkyrie taught the USAF, and NASA, much about + mach aerodynamics, and a host of other stuff.
cool concept..obsoleted by SA-2 systems by the time it actually flew.
But man...what a boss looking plane!
You might like this link, I stumbled across it this morning:
There are enough knobs, buttons, dials, and levers to keep even the most anal aviation geek occupied!