I was thinking about that myself. I'll test it out and post a reply on that. However if that's the case that's a very bad oversight and should be fixed soon, since Co-op is basically encouraged in this game but it turns out ruining your single player file.
@grimmshadows wrote:
Same problem here, except on PS3. Guess it's a glitch in the programing that tells if you join a game before the bot is avaiable it won't yet you have it then we you can have it, it's saved that you don't; and then if you replay the mission it reconizes that you've already played it so it assumes you already have the bot and doesn't give it to you again. One idea I can think of maybe if you play as Carver and join another game maybe when they pick it up for the first time you're get it again, doubt it but maybe.