The other day I went fighting on my own and summoned my Chocobo. Unfortunately I died. My Chocobo kept fighting until it eventually died too. I returned back to my last home set point. My Chocobo had a '???' status. I was in New Gridania, so I figured he hadn't traveled back with me due to location restrictions. However, when I moved to a zone where Chocobos were allowed, he was not there. I disbanded party and tried to summon him again with the greens. Alas, all the greens in the world couldn't get him by my side. LOL, my poor Sephiroth Chocobo... For a moment, I thought the game made Chocobos disown their pet-owners if they died in battle (what, with Chocobos being initially scared of battle until they gain the ability to fight through greens). Anyway, I went online and realized other players had the same issue. I ended up restarting the game. This time my Sephiroth Chocobo was able to return when I used the greens.

Anyway, just thought I should point this out and save other players from having to waste greens if their Chocobos are MIA. Hopefully, this bug gets fixed.