Oh my goodness, I'm just seeing this now. I am so sorry he got out, but I am SO happy you found him!! Poor guy was lost and probably searching for you
This is why all of my animals (cats included) wear collars that have contact information on them. They also ALL have microchips. It is so important for them to wear collars and it shows that you never know when they will get loose... Please consider putting a collar on Cooper. Just don't walk him on it, and he will be fine.