Is there any protocol for remote secret key storage without disclosure the key value for remote server administrator?
You could encrypt it. Just use a smaller key that you can memorize, and don't use the smaller key for anything else. Then if you need the larger key, you just pull it off the server, decrypt it, viola. If you're worried about someone brute forcing it because your smaller key is too short, you could try hiding it in a picture file, and then put the picture in a zip with other pictures and then encrypt all the pictures together. Bit of a red herring then.
Relevant question with a more refined answer: