I've worked in retail for years. Unless a customer has one of those "bigger than life" personalities, you wouldn't necessarily notice that a regular or semi-regular customer hadn't been coming in until someone pointed it out to you. This guy probably didn't come in cracking jokes or otherwise making a spectacle of himself; more likely he quietly paid for his Red Bull and slice of pizza and left. He was probably in often enough that they knew his face, but wasn't so notable that they missed him until they heard the report that he was perp in this case. At that point the reaction was probably like, "Oh, yeah, he hasn't been in in awhile."