This is a well-studied phenomenon of mental institutions: staff are acclimated to everyone in their presence being mentally ill and denying it. Consequently, th

This is a well-studied phenomenon of mental institutions: staff are acclimated to everyone in their presence being mentally ill and denying it. Consequently, they aren't exactly vigilant about finding exceptions. "The patient is lying and having delusions of grandeur" is probably an accurate assessment 99.999% of the time, so they are unlikely to doubt that assessment when the patient is in fact a researcher/journalist investigating the hospital.