So, I took the time to get to Level 2 in the Chaos covenant, and got to the special shortcut to Lost Izalith. As I was killing the bugs, I chased the crystal lizard up the stairs after the door a little bit and killed it before I killed all the bugs. The area title of 'Lost Izalith' did not appear. I went back down the stairs to kill the bugs, and Solaire already was hostile with the maggot thing on his head!
Is there a way to fix this, or do I just have to accept that he is gone for this playthrough? I'm really hoping that this isn't the end of my buddy the goofy sun knight!