To get the muzzle break on he probably "wiggled" it, rotating it left and right while pushing (or even whacking on it) it down. IF anything is going to loosen the grub screw that holds the barrel in place, this will. Will often tweak the barrel band at the same time. take off the scope, loosen both the grub screw and the barrel band, visulally center the barrel to the air tube, tighten everything back up again, and re-zero.
But there is another choice as well. You added weight to the muzzle, and that alone can change the point of impact.