ICT_SLB
The P.1109 fit that description; it was a German research-plane which the X-5 was loosely based on
Kitbag
the last paragraph probably answers the original question: the system used worked, but it wasn't very practical, I guess later systems/mechanisms were more robust but the aerodynamic data gathered was still very useful.
Okay, so the wing pivoted and what would now be called the glove, would slide forward a little over two feet in order to keep the center of pressure in place.
theficklefinger
Turns out during some initial testing as the wings sweep back, center of pressure moves back as well, and they lost some planes that were 'nose heavy'.
Hence when you look at your variable sweep planes these days, they have that fixed wing portion that extrudes away from the fuselage.
I believe that structure is called a glove (at least it's called a glove on the F-14) -- it's a wing-body fairing that the wing fits into (like how a hand fits into a glove)
It creates lift at a fixed point, keeping center of pressure at a fixed point. Extended from that are the smaller variable sweep portions, that being out so far don't seem to affect center of pressure so much as that portion of the wing doesn't create as much lift(less camber/less lifting area/less induced drag)
I'm not sure if that is accurate, as the X-5 had a glove too. As far as I understand, the center of pressure was retained by designing the wing so that as it pivots aft, some of leading-edge slides out of the glove (lengthening the leading edge, increasing lift up front); some of the trailing-edge ends up slides inside the glove (shortening the trailing-edge, reducing lift in the rear).
I gather they worked on a variable sweep wing that as it swept back, the attachment point to the wing, moved forward, to keep the center of pressure in a flyable place.
On the X-5, the whole glove slides forward as the wings pivot back; on later wings it would appear that as the wing sweeps back, additional leading-edge would slide out of the glove, whereas the trailing edge would slide into the glove increasing lift up front, and decreasing lift in the back.