hey I lost cicero for 38 skyrim days. I left him in the white phial mission. I hate to say it for all you lazy players and im happy to say this for all you dedicated players but you do have to go back. look in your mission inventory and try to remember which was the last mission you had cicero at. he is the only one beside Lydia I think that if you tell them not to move, they are never going to move. after you found a possible mission go back to that area. if you can't remember where it is look the mission up, the walkthrough. following these simple steps is probably going to be the most effective way to retrieve your lost companion. Just like real life, don't wait and hope for things to come on a silver platter. hope this was helpful.