Have you tried a trap? The lure should be something fishy, maybe even sardines tied to the cage so he has to pull on it and set off the trap easier without escaping. You may end up catching a few other creatures, but keep trying. While he may seem happy out there strutting his stuff, he could get into fights with other cats and end up with FIV or FeLeuk. If that happens, his chances of surviving become even slimmer.

I hope you are reunited with Gingin once again. Remember to keep the window closed.