Scientists are predicting that super massive black holes can not only be "bounced" out of their galaxies, but can be detected by the accretion disk that follows them. The event is supposed to occur when two large galaxies merge with two fast-spinning black holes in their center. The merging black holes would emit gravitational radiation along a specific axis, booting the thing in the backside to the tune of perhaps ten million miles per hour (~ 15% of the speed of light).
Assuming the accretion disks are going much faster than the now larger and moving black hole, the newly merged disk should travel along with it "like sheep following a shepherd," being bright enough to see for perhaps several million years. Even then, the objects would still be quite difficult, but not impossible, to detect.
After that, one presumes, it's completely invisible, and perhaps impossible to track as it barrels through space, gobbling up anything unfortunate enough to be in its path.