That is awful! Who steals chickens?!
Apparently lots of people do.
You won't find me in the group of people who refuse to believe there are nincompoops out there that would do such a thing. I am still so very sorry this happened to you. It realy should not have happened and you have my complete sympathy.
Talk with your parents and if you decide to replace your flock try and increase security before you get more chickens. It is usually not too hard to enclose, and add hasps and locks to all runs, coops, egg doors, and other large openings. Heavy hardware mesh is hard to cut and handy to cover vents. Food and supplies should be unavailable for tampering as well. If it is possible, and you can afford it, add a motion light or two. It has been shown that motion sensing lights coming on is one of the most effective deterrents to this type of criminal activity.
I live in a pricy (but apparently disfunctional) area . I have neighbors who feel entitled to run your yard, and your home, their way. If they cannot legislate against you they simply take matters into their own hands.
Some feel they are protecting their property values.
Some feel they are protecting society, or the environment.
Some of them just don't like animals.
I know of one neighbor who "rehomes?" anyones pet cat she can catch. She fancies herself ecologically aware and superior. Her take on the matter is that the songbird population is being decimated by other people's pet cats who are "killing machines". Ditto dogs who "kill deer in vicious packs". She is quite open about this and everyone knows who she is, but it has proven impossible to press charges.
In addition to this nutcase, we have the immuno- compromised contingent who are terrified that your pets, especially your chickens, will spread disease, contributing to the next major catastrophe, which will undoubtedly be an aisian flu epidemic.
I am somewhat more sympathetic to someone hungry who steals for food. But only a little as most everyone hungry has easier and more effective ways to get a meal, than stealing, killing, and cooking, someone elses chickens.
Again, I am so sorry that this happened to you. Most people are good, and kind and honest. Even if it does not seem that way it is true. It is just that good people are often quietly going on with their lives and you so rarely know they are there. The truly disfunctional types are rare, and we should pity them without getting caught up in their issues. Your life is still a good one, and this too shall pass even though it may not seem like it.