I have a couple of thoughts on the topic based on my experience with a pink spotted goby and a candy stripe shrimp we've had for almost two years now. When we introduced the pair, they quickly disappeared under the rocks and it was very rare to ever see them. In fact, I've literally only ever seen the shrimp one time since that day, and the only reason we know its still alive is the snapping we hear a few times a week. The goby sightings were very rare until a few months ago so we started calling her 'Nessie', as in the Loch Ness Monster, because in the beginning, the sightings were few and far between and when you did catch a glimpse it was just a blur as she would dart back in the burrow.
So what changed - A few months ago we donated our Cowfish to a public aquarium because she was pushing 10 inches in length. Within a week of removing the cowfish, we started noticing the goby out all the time and she sometimes ventures out and around the tank now. While the Cowfish was not aggressive towards anything, I can only conclude it must have been the size of the fish that scared the goby and keep it from even showing its face, even at the burrow entrance. So if you have larger fish in your tank, you might consider looking for a bigger goby or asking around to see if anyone has one with larger fish. You might find certain types have a better track record in larger tanks with bigger fish. Just a thought...