Please, to other members on here who are posting, try to be as understanding as possible. Even though the situation may be frustrating, no one is going to listen to anything if it's said aggressively or in a way that could be perceived as aggressively. And that's a proven fact of human psychology. If you want someone to listen and if you truly want to help the original poster and their CoCo, calm and understanding tones are needed to get points across. Causing more unrest will only make the original poster not want to listen to you, and it puts your own feelings and want to be the person who's correct in this situation before the safety or wellbeing of the bird you are trying to help.
A language barrier can also cause escalation because it causes more misunderstandings. If you truly want to help the birds and person involved here, try to remain calm and understanding so that we can all effectively communicate and listen to each other. Although the situation is not ideal, pointing out all of the flaws and non-constructively criticizing them is not going to help anyone.
@Armin I would strongly recommend you do not get another bird in your situation. Another new bird, especially a senegal or african grey, will just add to your current stress. You truly seem to care deeply for your CoCo and I can completely understand why you are upset and angry. You've just lost your friend and he hasn't come back. But please understand that CoCo did not do this to hurt you and not because he doesn't care. He probably flew outside because he was curious. But then didn't know how to get back. Many birds don't know how to fly down from trees and he was probably very scared which is why he didn't come to you.
Bird's are not very obedient animals, and they are wild animals that will choose when they want to listen. Senegals and african greys are just the same, they can learn but they will choose when to listen. Coco had lots of fear in that moment and that likely got in the way of him listening or being able to come back. You might set his cage outside if he's still around, because he will recognize it and may try to come down to it. But please do not get another bird right now. I know you love CoCo very much and want to get another bird like him to be your friend, but senegals and african greys are very different than cockatiels. The frustration of trying to live with a more complex parrot will likely only add on to your current grief.
Also, do not let any comments here discourage you. I'm deeply sorry if any other members have upset you or offended you, many on here are simply very passionate and worried about the care of parrots and they worried for your CoCo just like you are worried for him. We all care a lot about parrots and want to help improve their lives, but I believe we became frustrated and confused which caused arguments. There are many members on here who are patient and understanding, please don't let a few replies discourage you from returning or asking questions on here.
I hope you stay on the forum even after all of this. We all love parrots on here and you have shown before that you care, too. We want to help educate you and answer any questions you have, just like the questions you asked us about CoCo. You clearly wanted to improve his life and care, but please stay on the forums and learn more about parrots before you buy another. Parrots are difficult animals to live with and they are not domesticated like cats or dogs, so that adds to the complexity of their care.
But there's lots of information on here and hopefully we can all talk effectively, even with the language barrier. If you want to get another companion, please do more research or ask questions about species you're interested in, we've got lots of good information and good people on the forum here.
I'm so sorry for your loss of CoCo and I hope he makes it back home.