While we can't see him and be able to say, he is right there - However, the last time they saw him he was unmistakably heading home to his father! Do you think it was crucial that Jesus' resurrection was witnessed? Certainly! What if he left this earth with no witnesses? Perhaps it would have been as in the days of Elijah, they continued their search for him. The ascension in a sense is the climax to the incarnation! That which they had heard, seen and touched was now seen returning.