I was successful in reuniting a family member with a child given up for adoption in 1960s. I simply posted on every available registry. A few months later, the child started looking and found the match right away. There was a lot of luck involved, however.
You have a great advantage in that you have each other’s names. I would try the registries just in case she is looking for you as well now that your daughter is 16.
If that doesn’t bring results pretty quickly, find a private investigator or just someone who can run a credit report or something which should have a current or at least recent address.
Best wishes!