I think with so many clients going through the office in a day, if no one was scheduled for T during the time you were seeing pdoc, T was probably just concentrating on whatever task they were doing, not expecting anyone so not looking around. Next time call out a "Hello T"? I would do as WePow suggests and let T know you missed being seen, maybe joke and tell T next time they're going through the waiting room and you're in it, look for you.