What is the process in finding out if my daughter was adopted by her step-father when I was living out of state at the time?

I am guessing you are the biological father.
You would have to have signed over your rights in most cases. If you didn't chances are most likely he didn't .

Check with the court house where he is living, if he says it happened require him to prove it.

Next it would appear this means you have not seen your child for some time? Did the father have custody at the time ?
Are you wanting to visit ? I guess I want to know why you are asking ?