That depends on the circumstances of the custody modification.
Was it permanent, temporary, was the child adopted, did the parent
voluntarily relinquish parental rights or were they terminated by
the court? No one here can possibly give you an answer without a
lot of detailed information including your legal residence. You
should really consult an attorney anyway. He or she would be able
to provide an informed and detailed opinion on whether or not you
have any rights and if so, what they are.