I'm so very sorry about your loss. Unexpected death is the worst.
On December 1st, I lost my Papaw. He was only 74. This last year, DH and I built a house. Papaw worked so hard on it. He built the foundation baskets, hung the closet rods, plumbed, painted, etc...We never even knew he was sick. I saw him early that morning. I took off from work because DS was sick. DS and I planned to snuggle and watch cartoons after sleeping in, but DH woke me up to say our Christmas tree fell over in the night. After cleaning up that mess, I was unable to relax. DS was awake and cranky. I saw snowflakes falling out the window and took DS to the French doors in our kitchen to look at them. Papaw was in the yard (he lived next door) doing some work. I watched him to make sure he was okay but did not speak to him. Around 11:15, DH came home for lunch and saw Papaw walk back from his garage to his house. By noon, Papaw was gone. He went in, ate lunch, sat in his chair, and that was it. I grieve because I didn't talk to him that morning. I didn't know it would be the last time I saw him.
I'm glad you got that last talk with your dad. My prayers are with you.