Go ask the building security guard.

Whoever delivered the packet, the security guard would have seen them. After throwing some decent clothes on, putting the credit card in your wallet, and making sure you have both phones, you head downstairs to ask him.

Stepping into the lobby, you see that Tony is on duty this morning. He looks up with a smile and waves at you. "Hey, man! Congrats on the new job!"

"Thanks, Tony," you respond, approaching his desk. "Honestly, I still can't quite believe it. Actually, did anyone unusual come in this morning?"

Tony furrows his brow and shakes his head. "No, it's just been tenants in and out so far today. Why?"

"No one you haven't seen before?" you ask incredulously. How can that be? Someone dropped off that packet. Was it one of your neighbors, somehow? "Someone dropped a packet about my new job in front of my door. You must have seen them, right?"

Tony stares at you for a moment, perplexed, before shaking his head again. "I don't know what to tell you, man. I've been sitting right here since six, and the only people in or out have been people that live here. Maybe it had been sitting there a while, and you just didn't realize it?"

"Maybe..." you concede skeptically. "Thanks."

It's not a lot to go on, and a part of you is starting to think it's better not too look a gift horse in the mouth.