PhDinCoffee

Hello, So a little background. I am looking to apply for the 2018 cycle for a Ph.D. in Biology/Biomedical Sciences. My PI I did undergrad research with (and got an A in their class) and I have been talking since 2015. About a year ago now, I expressed my interest in applying for the Ph.D. I asked him if he would be willing to write me a letter, he said yes but did have reservations in earlier meetings on me going for my Ph.D., period. Anyway, I took a gap year and worked in industry which further solidified my route to grad school. I have recently e-mailed him again for a meeting to talk about the LOR he said he would write. The last time I had e-mailed about it, I visited him when I didn't receive a response and he said he never got it which was strange because I sent it to both of his e-mails and he seemed to always get my e-mails just fine in the past. Anyway, so I recently e-mailed him again (I am out of town so can't visit) and I haven't gotten a response yet which is fine but I'm wondering if it would be acceptable to follow up with a reminder/nudge on his LinkedIn account (which he has messaged me on before) and message him, just in case he didn't get my e-mail again? Is this acceptable or no? He is my best bet at grad school admission because I did research with him AND did well in his class so I really need his letter. If it's ok to contact via LinkedIn, is this an acceptable way to go about it? "Hello Dr. X, I just wanted to let you know I am applying to grad school for this upcoming cycle. I sent you an email regarding a request I had for a meeting along with additional information. Please get back to me at your earliest convenience. Thank you deeply for your time. Respectfully, Annoying Student Y" I don't ever want to come off as annoying or disrespectful to him so I am getting really anxious about this and wanted to ask you all to see what you thought. Thank you in advance!!