I don't think they moved or were taken. It appeared that the rocket took off from the corner of the pad and landed in the center, with one camera angle for the corner launch and one camera angle for the central landing. So, I assume the risers are still exactly where they were, they're just outside of the camera frame.

If you look at the landing shot, you can see that towards the corner are some markings for previous risers which were used for previous launches (or markings for future risers for future launches). The risers it launched from this time are just in a different corner.