Some people with meat birds they try to keep longer will limit their feed intake and let them free range, so they do not gain too much weight. So sorry that this happened.
Getting an accidental meat bird happens way more than it should. They are usually labeled by breed, in feed stores, but...
Sorry for your loss. I would agree that it would be possible that your dead chicken was a meat bird, a cornish cross. Occasionally, these birds are accidentally bought by people thinking they are egg layers. Meat birds are typically meant to be butchered around 6-8 week old, and if they are kept...