I've done this, so it isn't completely off the table. I did follow this up by sending him a thank you note via US mail too. I would send a thank you e-mail to the interviewer if he/she provided you with their e-mail. IMO, it is a bit presumptuous to look up that person's e-mail on the internet and then e-mail them.
If it is any comfort, I was accepted to that school also.