Alright. My opinion is that while Squall was alone on his little island of hopelessness he began to think of the one person whom he loved and gave him hope. The visions of Rinoa dying (the faceplate of the helmet breaking) was meant to crush Squall's spirit. (This vision was the scariest because it was the one time that he thought Rinoa was going to die so it was easiest to believe.) Seeing her die and believing that she was dead made Squall give up. Therefore he passed out right after that vision. He could withstand all the other crazy visions but her death was the last straw and he gave up. I also think that Squall got seperated from the others because his subconcious was concentrating on other things. Such as his childhood when he was alone, Edea, and what happened to Ultimecia. He wasn't able to find his way back like the others because he had things yet to do. Rinoa thought of how she wanted to go to the place they promised to meet so she went there. After a while she got worried and wanted to be where Squall was. Hence she ended up in Squall's desert. When she found Squall she wished that they could have met where they promised and the time compression ended and they ended up there.
