They went out from us, but they didn't belong to us; for if they had belonged to us, they would have continued with us. But they left, that they might be revealed that none of them belong to us.

 This was not so much knowing God as feeling God. But it was a highly emotional experience and, as such, it was necessarily transient. It was a kind of religious drug. It quite definitely found God in an abnormal experience and its aim was to escape from ordinary life. 