I was too slow to manage assisting one of my so-called "friends" in a shoot-out after completing a blue mission. Now his status is "missing". Can you find missing buddies again or are they lost until there's a plot twist, or will they crawl back to Mike's bar once they get thirsty again?
I think it's just luck if you find them again. Do all the flashing safe houses and you'll find him/her again. Sometimes you never find them again. I have 4 "abandoned" buddies but I never intentionally screwed them, they just ended up being labeled like that. I don't think you can be 100% in good standing with all your buddies.