That really sucks dude.
About a year and a half ago, I started missing some packages in my apartment building. The mailman comes while I'm at work, so when he's got a package that doesn't fit in the mailbox (which is quite small, as it's a large bank of slots, one for each apartment), he just leaves it in the hallway by the stairs, near the front door, where everyone walks by.
Well, I noticed some packages never seemed to arrive from Ebay, despite the sellers claiming they had sent them. At one point, I lost an expensive collectible - a Dark Knight Joker Poker set - and that's when I decided someone must be stealing these packages after the mailman leaves them.
Turns out I was right - a few months later, I noticed a flurry of hand-written signs taped on the wall of the hallway, from other residents demanding that people stop stealing packages and asking that they return them. I guess one person had had enough and posted a sign, and someone else saw the sign and realized it was a building-wide problem and not just them, so they posted a sign, and so on.
So the problem affected all of us. Of course, the signs were gone within two days - either the landlord took them down (either because they weren't aesthetically pleasing or because he didn't want tenants and prospective tenants to become scared), or the thief felt guilty and tore them down himself.
Anyway, after I lost the Joker Poker set, I started having all packages routed to my girlfriend, since she lives in a house with roommates, not an apartment building with a lobby and a bunch of strangers. She's moving now, to an apartment building but I learned I can route packages to my workplace instead now, so I'm just going to do that.
What really bugs me is why the mailman thinks it's acceptable to leave packages on the floor like that. Leaving it in a public hallway, where plenty of strangers walk by each and every time they enter and exit the building is NOT acceptable - it's no better than leaving it on the curb of the street. If there's no office to leave it with, the US Post Office should, by policy, leave a slip asking you to schedule a redelivery or pick it up at the Post Office. But I guess some of them are too lazy and don't care enough.
I hope you get your package back - but common sense (and previous experience) suggests you won't.
Either way, I'd consider finding an alternative destination for larger packages - because even if they had left it in front of your door, and not your old apartment's door, someone could have just as easily taken it as they walk down the hallway. A friend's place, your workplace, or even a mailbox rental place - it's all better than a semi-public hallway being used as your mailbox.
