Signs. One sign is pulling away from others. Lack of emotional intimacy with loved ones. Emotional numbing. These symptoms can quietly destroy relationships.
PTSD hints. Some subtle signs might be a generalized numbing to all experiences, and avoidance of stimuli which could remind the person of the traumatizing event(s). Friends and family might notice that the person "just isn't the same", even though s/he may not be speaking about the event.
Symptom inquiry, yes. The doctor should inquire if the patient has been in a situation where the patient believes loss of life or catastrophic injury was imminent, and with no means of escape. Symptoms from these experiences include, hypervigilance, sleep loss, nightmares, reliving the trauma, social withdrawal, anhedonia, temper outbursts, emotional withdrawal, feelings of unfinished business, and adrenalin seeking.