What a great story!
This same thing happened to my aunt. It hadn't been 7 years, but it had been 2. Her cat Smokey was an indoor/outdoor. One day he just disappeared. My aunt was heartbroken; he was her baby.
She and my uncle moved, but she continued to go back to their old house (same town) periodically and call for him and search the area.
Well, my OTHER aunt kept swearing up and down that she saw Smokey, and we all thought that she was insane. But she kept taking that same route where she saw him, and lo and behold, she caught sight of him one day, pulled over, and was able to catch him! She returned him to my aunt, who kept him indoors for the rest of his days.
He lived to a ripe old age; in fact, the poor little guy was just PTS this year, bless his heart. My aunt was heartbroken. She hasn't gotten another kitty yet; she says that she never will, because she can't bear to lose another one