At this point I believe you would have to rely on the fact that he would immediately know you and come to you, and identifying marks, scars, pictures and words/tricks and things you taught your grey that would identify him. Do you have an avian vet for Sindbad? When I purchased my grey, I was given a bill of sale, I assume you were also. Of course, none of this is important until you find Sindbad. Still praying daily for his return!