2 Kings 2:16

Let them go. The sons of the prophets had seen Elijah departing with Elisha and they had witnessed Elisha’s return alone, clad in Elijah’s mantle. Before that they had had a revelation from the Lord that Elijah would be taken from them. God had probably not revealed to them the exact manner in which Elijah would be taken, and perhaps they had not been permitted to witness all the details of the ascension, at least as clearly as Elisha had. But Elisha probably told them what had occurred, and that should have been sufficient. Perhaps they did not understand, and thought that the body of Elijah might have been deposited upon some desolate mountain height or in some lonely valley in the regions across the Jordan.