When I was out of town my land lord came to my house to "repair" something and in the process let our indoor family cat out in which its been 4 days with no return. We nursed this cat back to health when it was a kitten therefore it means a lot to our family. HELP! What can we do?

Cats have a way of sneeking out when a door is opened... even when trying to keep them in. The fact the cat wasn't sitting at your door for four days now tells me it was one that really would have tried to slip out given a chance. If you try to bring any action this will be presented as such.

You are aware YOU have to prove it was intentional and not accidental. And that stirring up trouble might result in a landlord that might not want to renew your lease when its up for renewal.

Pets, I discovered years ago, are considered property by insurance companies, so the most you can get is the value of the cat, depreciated. I KNOW that's absolutely horrible! Don't shoot the messenger. I love my dog and my cat, and I hope you are scouring every neighbor's garage and putting signs up everywhere, and I hope you find it.
Courts also listen to the whys: it really sounds unintentional.