Concorde thrust reversers engaged on parked aircraft, but not all engines?
Yes the left (#1) reverser is engaged in this photo. G-AXDN is the British pre-production Concorde and has some differences from the final versions. G-AXDN contained internal clam shell reversers, if the GIF at the bottom of this informational page about G-AXDN is any indicator that external engine reverser may still actuate for show and in this case was simply closed while you were there. This video shows the light up ring that they may have used in the GIF (5:02)

This Concorde also has a droop nose that still works. There is also a fairly active effort going on to restore that airframe to have some of the parts work.