THANKS FOR REFERRAL
I would like to thank you for your referral to [FIRM, ex. ABC Co]. [MENTION WHAT OCCURRED AND WHAT YOU WILL DO AS A RESULT OF THE REFERRAL, ex. On your suggestion, I have spoken with Mr. Holmes and forwarded my resume to the human resources department. I hope to be hearing from them soon.]
I will keep you up to date as to what happens. Thanks again.