I think a hen is worth $20.00 - $50.00+ each depending. 12 hens = a min. Of $240.00 to what ever more. They were "rescued" by person unknown with the add of the landlord, that is THEFT. Call the police, report a theft of personal property. I am not sure, but! Arizona still has laws, not yet removed, covering livestock stolen. Check into it, you may be surprised. The laws in this state, around live stock as a ranching/range state.
I would call the police. Use the system.
I am not trying to defend the landlords actions, but.....
It may not be 'theft' if the following are true:
1.) The chickens were illegal in that city. (if a tenant is in violation of the law, the landlord has certain additional rights and responsibilities to correct the violation)
2.) The landlord must notify the tenant 24 hours in advance of entering the property...if he did not enter until 2 days later, he could have posted a note on the front door of his intentions to enter the property the day (or 2) before, therefore he was within his legal rights to enter the property on that day.
3.) If the there is an emergency (such as animal safety), the 24 hour rule is null. So if a neighbor contacted the landlord to say the tenants left on vacation and their animals were not being attended to, and the landlord found them to be out of food, water, or in this heat without adequate shade, then again he was within his rights to allow the animals to be rescued.
I have no idea if any of these apply, just wanted to be fair to both sides by mentioning them. Landlords (yes I am one) tend to get a bad rap in many situations when the tenant is at fault, like for example when a tenant spends all their money on partying instead of paying rent, then after eviction they feel justified in tearing up the place and leaving it a pig sty.
So, with this said, IF your chickens were legally there; had plenty of food, water, shelter, and shade; a neighbor was taking good care of them in your absence; and having chickens was not a violation of your lease, then the landlord was in the wrong. I hope the chickens are safe & sound back at home now, I sure would like to hear a happy ending to this tragic story.
That is exactly why I believe in gathering all the FACTS Possable. One you have the facts you are well armed. It is time and energy consuming to check and gather data, but it is worth it. You said you had arrangements to have your girls taken care of. Check it out, were they? If you were paying this person, this is a big point. They are then responsible, in part. You said your landlord may have been contacted by a neighbor, this is important. 1 more piece. Once you have all the facts/data, look it over, then decide the next action. Chick the laws, were you in compliance? Be mindful that your little flock has value. Average market value for a hen is $20.00 min., more with other factors taken in. EX: Difference between a mutt and a dog from champion blood lines. If you got your hens from a breeder they are worth more the $240.00.
Win the landlord to your side, you are a victim of misplaced trust. Earlier you were consumed with emotion, grief, and shock. You have been doing your home work and you understand his point and appreciate that he was only thinking of saving your hens from suffering. You, yourself, would have been inconsolable if you found then dead of neglect rather then rescued. Depending on your landlords temperament, it can't hurt. Make assurances that reliable custodian will be hired in the future. You will have someone, a neighbor maybe, that will have your number so if they are not being cared for you will know. The your landlord that the next time you leave as you did, you will notify him, so if he gets a call he can let you know.
How you approach things is important. When I had my accident, I got all my facts, waited several days until I was calm and in control. I went to AAA, told my story, presented my facts, and talked to the AAA representative as if she was only their to help me resolve a problem that caused my accident so they are better able to take care of their customers. I succeeded, she is the one asking on my behalf, for the deductible on my car repair. At the same time, when speaking with the regional manager, I let him know that I was not out to ask for more then what is right, as failure in AAA contract with members. I did not say, but tried to let him know that I was a ware of lawsuits won similar to mine.
I had to learn all of this the hard way over the years, with advice coming in retrospect.