I have just read your entry. I am sorry that you haven't had anything you could call proof of your grandfather's presence. I would however take your Grandmother up on one point. There is no such thing as coincidence. Keep talking to your Grandfather he can hear you!
It takes much energy for a spirit to materialise you know. He may well be there but you may be looking in the wrong place.
I often feel my father who passed over in October 2003. I can smell his cigarette smoke, I catch glimpses of him in shop windows but when I turn to look he isn't there.
Be secure in the knowledge that your Grandfather is now in a much better place and free from all pain and worry.
Love and Light