Have you considered calling Bill Murray? I think he may have some clay "friends" to introduce to your gopher.
(And, yes, coincidentally I just recently saw that movie for the first time)
In all seriousness, I'm not sure what you do about the creature. We have wild boars and moles that dig up our lawn, and we can't get rid of the things. You can try calling an exterminator, perhaps, but I think the only way you can get rid of it without risking it returning is to have it killed. Or you could just live with it, as we've had to do.