You know, I keep considering the option that there was some verbal fight and separation. Later when he finally returns, she is nowhere to be found and he drives home thinking she left him BUT... There seems to be texts and social media activity after the time we think she died, such as the text to her mother on the 30th? I don't think there's enough room in the timeline for her to still be alive on the 30th and then him driving home alone by the 1st...
Most people take their phones everywhere so if BL did take off, and GP was sad and someone tried to console her. She probably would have taken her phone with her. So whoever hurt her could have had it and them mistaking Yosemite for Yellowstone even more likely. I don't want to give BL any more alibis but I would hate to find out that he hurt himself and he was innocent. Can you imagine how much that would compound this tragedy? I know it's stretch.