Warning: The following is just a theory!!!
Okay, so Shannan and her driver arrived at Oak Beach at 2 am. Here's what I think happened after that. I think that either Shannan wanted drugs or someone else at the "party" suggested they get some drugs to get the party going (maybe adderall or some other RX upper) and Shannan agreed. Then maybe JB said something like "my neighbor is a doctor and he can help us out, let's drive over there, it's just around the corner."
So Shannan and JB drive to PH's house to get some pharm drugs. However, the pills they get are not what Shannan had in mind and instead she is provided with roofies or something of that nature.
The phone call to CVS was at 2:55, likely when the pills started kicking in and Shannan realized something didn't feel right. Maybe she was scared and wanted to call 911 at that point but JB or the Doc said something like "you're probably just be having a bad reaction, nothing to worry about." So in her altered state, she decided to call the nearest pharmacy to ask them if the pill could be interacting with her bipolar medication (or whatever). While trying to make that call, someone talked her out of it and she hung up or someone took the phone from her and hung it up (that's why the call was so short).
Beginning 2 minutes after the CVS call, Shannan's phone makes and receives 6 calls to and from MP until her 911 call at 4:51. If it was Shannan making these calls (I believe it was, for most of them), then clearly she knew something was horribly wrong. What was she saying to MP during all of these calls? How come he didn't come see what was wrong until JB called him?
So Shannan was drugged and incapacitated by the end of the evening. She encountered an actual danger at some point but due to her incapacitated state, was unable to coherently explain what/who she was of to anyone who tried to help her (i.e.- GC, 911 operators). She began to perceive everyone as a threat and ran and hid, until whoever was actually after her (likely the person or persons who drugged her) eventually caught up with her...
That'll all I've got right now, feel free to tear it apart.
I can't believe Shannan has been missing for a year now, I pray that her family finally gets some answers soon.