You did it right. You're correct that the crew probably doesn't really care, or maybe they were just busy or having a bad day, but it's the proper etiquette to make the attempt and let them know you're back there. The only times I've ever skipped the intro was when squeeking on just as the door was closing and the F/A's are rushing everyone to sit down. In that case, I still say something to the lead F/A and then thank the cockpit crew when deplaning.