Gobie and Shrimp Pair Question

[reef bound]

We had a yellow watchman in our 34g Red Sea Max and the little turkey decided to dig to make his home right at the back of the tank, never to be seen. We added a pistol shrimp a few weeks later and they found each other within minutes and the pistol started digging at the front of the tank and they lived happily ever after. We saw them all the time. (But really, I think it's just luck that he dug at the front). We moved them to our 180g and we haven't seen the pistol shrimp since, but the goby has made his home under a rock at the front of the tank. I know, makes no sense.