Word to describe belief in God
Solution 1:
If someone believes that God went away because God died, you could call this belief theothanatology (and thus perhaps call the person a theothanatist - this concept has been put forward by some philosophers and is explained on this wikipedia page
https://en.wikipedia.org/wiki/God_is_dead
Solution 2:
The word you are looking for is "deist". Essentially, they believe that god created the universe and that's about it, neither interfering in nor caring about human affairs and not required to sustain the universe in operation.