I found Charlie Cat thirty minutes after writing the last post.
Unable to sleep, I got up and looked out the window at the back porch, hoping against hope that I would see Charlie Cat eating the food I had put out. He was not eating the food. He was slinking across the porch heading towards the back yard.
I hurriedly opened the back door. "Charlie Cat, is that you?"
Charlie came running into the house. He was hungry and thirsty but before he would eat, he enthusiastically butted against me, mewing and purring in pleasure.
It is now 4:20 AM. With any luck, I'll be able to get a couple of hours of sleep before I have to head out to the airport ... but at least I'm leaving with a glad heart knowing that Charlie is alive and well.