Husband born 8-02-1973 ISO birth mother

My husband was born in Great Falls, Montana in August 1973. He was raised by his birth father, but his birth mother left. Eventually he was adopted by my FIL's 2nd wife. We are now trying to find his birth mother. On the birth certificate from Deaconess Hospital her name is written "Pattie Jo White." We've been led to believe by relatives that her last name may now be Trimmer. However, the address they gave us came back. Part of me wants to believe that his extended family doesn't want him to find her. I feel like he's really been given the run around any time he tries to get information. But it was an address and the people there were gracious and kind enough to send his letter back and tell him they don't know who she is. Any help would be appreciated. You may post here or email us at era0307@yahoo.com