Why would the location of a dementia patient now be suddenly considered confidential, with visitors now needing to call the fiduciary's office first?

Patient Privacy: A patient's location, or even whether or not they are in the hospital, is considered private, and the patient (or their legal representative or decision-maker) can request this information is kept confidential. Sometimes different areas within a hospital (icu, behavioral units, etc) each have their own separate standards and policies about sharing patient location or details as well.

Nursing home?: In a medical or healthcare facility, especially on a locked unit for alzheimers or dementia, privacy takes on a new level due to the dangers of wandering behaviors and possible exploitation and vulnerability. Fiduciary offices, i'm not sure about unless there is a power of attorney for healthcare and a list of approved visitors has been provided.

Depends on details: Privacy and concerns regarding potential exploitation often are key to these types of decisions. However, most states have ombudsmen who work at facilities. You can contact them if you have concerns.