Please, don't give up on Captain Jack. Kittys sometimes get wanderluster and go off on "secret missions" known only to them.
We had a Chow-Chow once (she has passed over the rainbow bridge) that would "go for walks" in the neighborhood. Although she wasn't allowed in the unfenced front yard, sometimes she would slip out. The first time she was gone for 10 days, the second time for 3 days. After the second time she somehow knew that if she turned to the left or right at the end of our street she would get lost, so she would go to the end of the block, cross the street and them come back on the other side. LOL She was a hoot, I loved Sassy, and still miss her tremendously after 10 years!
Come home Captain Jack, your mamma is missing you!