Another question, what would happen if a pure blooded noble dragon somehow went missing as a child?  Would a family of common dragons even take it in? Would they be able to tell whether or not it is noble blooded?

What I meant by what would happen if it went missing is that would there be an extensive search that would last years? Would they eventually give up and assume that the child died?  In this scenario when he was still a baby he was swept away by a river and raised by a family of commoners.