riss11, i don't know that i would facebook msg someone... not for any hard rule that i can think of but just.... meh? i am just starting to shadow. for one of my shadows so far i needed to go cold like you - i want to shadow a PCP which requires leaving my better connections at an academic center.
what i did was write a letter and print a hard copy, directed to the doctor him/herself. i googled to find these people. one of them i chose because she had a mentoring award listed on some site, which made me think she could be more open to having a shadow, and lo, she is the one who has emailed me (will see about the other, dropped them off less than a week ago). the point is that i dropped off the letter in person, i think based off advice i saw on sdn. i wanted SOMEONE to have a tiny bit of interaction with me in addition to my written letter. dunno how much effect it has, but looking up info on potential docs and also taking a letter directly to their office to go in their mailbox at least gets your info into their hands, and not into the inbox of some nice but overworked office assistant who gets 400 emails a day..
i also don't know if this makes any difference, but i did make sure to give a bit of background as to why i wanted to shadow, why that particular area of med, and i made sure to mention that i had observed at our academic ctr too, had hipaa training, and that i understood the professionalism required etc. obviously it's my word and if they want me to do their hipaa that's great, but they know i've thought about it and that i have been in a similar situation. if you haven't observed before but did hipaa to do your clinical volunteering, same idea. i wanted them to know how little trouble i would be 🙂