The Bible says:
"How you are fallen from heaven , O Day Star, son of the Dawn." (Isaiah 14:12).
If he is not in heaven, then earth is the only other place I know of that he could be. In fact, the Bible verifies this:
o "Be sober, be vigilant, because your adversary the devil, as a roaring lion *walks about* seeking whom he may devour." (1Peter 5:8)
o "And the great Dragon was thrown down, that ancient serpent, who is called the devil and Satan, the receiver of the whole world --he was *thrown down to the earth,* and his angels were thrown down with him." (Revelation 12:9).
o "...Your adversary the devil *prowls around* like a roaring lion, seeking something to devour." (1Peter 5:8)