there are some denominations, SDA is one at least here, some branches of Baptist are another, who do not follow a uniform policy regarding baptism. Either they don’t adhere to the directives of their own body, they do not accept all the beliefs about baptism propounded by their own body, or they are splinter groups or pastors who have their own views and conduct baptism according to them. For that reason, even though SDA baptism is listed as “generally believed to be valid” we are further instructed to examine each and every such baptism and ascertain the facts. If you were old enough to remember, or have witnessed who can attest to what happened that will help, but the diocese will also have knowledge since they have investigated how a given denomination or even a given pastor in your locale actually does practice.
For that reason your director is right to go with the information provided by the diocese, but that does not let her off the hook with regard to investigating your situation. In a case such as that OP describes most likely he would be baptized conditionally, unless the facts surrounding his baptism can be proven.
Even if that becomes necessary, it is no reflection on OP, simple a quirk of human nature, that someone or something he thought he could trust turned out to be not what he expected. None of that would be his fault, there would be no whisper of blame on him, the experience of being shaken up by the situation is part and parcel of the process, and I hope his director helps him with those feelings.