Who Should I Follow Up With…? (serious Question)?

I’m applying for a dog guide instructor position. When I was in school, I had a preliminary interview with the Director of Programs. He made me aware that if I were graduating that school year, he would of taken me on in a heartbeat. I graduated, and saved up a little money at my job as a dog trainer at another place. I applied again, with recommendations from my friends/professional relationships. I sent my resume to the head of human resources, she in turn, gave it to the person who would be my supervisor. I went for my next step of interview, in October, with the lady who would supervise me. After she discussed the position with me, she said to email her the next day and let her know if I was still interested, which I did. The position I was applying for would start in February. She also told me that there would be 6 more opening over the course of the year, not to be discouraged. During my interview that day, she wanted me to meet with the Director of Programs again. He had a workshop to attend so he didn’t get to. Needless to say, I didnt get the job (it went to someone on staff who had worked there for 3 years). The HRM has emailed me, and had told me to give my dog a hug. Well, my friends who work there, said don’t forget to be persistent.. they need the people..etc.
So, my question is who should I be persistent to?
The Director of Programs who told me I would of been hired at my prelim if I was graduating?
The HR who I’m on a good accord with?
Or my potential supervisor?
I’m thinking the director of programs.. but I wanted opinions!
Thanks so much!!
(Please, any negative remarks will be taken as abuse).