I'm sorry you have not had much luck either. Can you trace the Clark lineage at all? Do you know any relatives still living to provide ANY information?
The person I'm searching for is quite removed from me, was a baby girl my great grandmother gave up when she was 15. I think I found the baby listed in some files at the University of Idaho, in the North Idaho Children's Home collection. But, no real way of knowing.
Good luck to you!!