So, I just remembered that I should've gotten Coby's number, yet I don't. Now, this is a 0.4 save, where I finished Seth and Skye, while I tried to get into Dustin's. This is also the save. Dunno why I added this.
Stupid question: Did you already play through Coby's "Date"? Once you had the sexscene with him, you should have his number to restart the scene if you wish.
Coby's number is unlocked after you finished the prologue, looks like something went awry there. Did you manually mess with your save per chance?