If you were to write a first-person account of a hypothetical ending of the book, it might go like this:
At first, everyone in the community is confused that I am gone. Once I leave the outskirts of our community, memories start drifting back to the people. They realize that I am gone for good.
Chaos ensues. They are not prepared to deal with the memories. Suddenly, they have memories of pain and suffering. They feel hunger, they experience death. They also feel love and happiness, but they do not understand that either.
The elders turn to The Giver for help. He guides them through the emotions that they are now feeling, and explains to them that these feelings will have to be a part of life from now on. There is no time to train a new Receiver of Memory. The community must learn how to cope with feelings.
In the meantime, Gabe and I get farther and farther away. We use what memories we have left to sustain us, but we are running out of food and getting colder every day. I realize that we might not make it. I know that Gabe would have died anyway, and I am happy for his last few days of life. But I am sad to see him go. I know that wherever he goes, I will follow him soon.