Lost phone

I lost my phone (T-Mobile G1). The last time I clearly remember having it was around noon, in the 3rd floor men's room in the MIT student center (near our MIT Mystery Hunt team's headquarters), and it's quite possible that I left it there.

I'm not sure what all I need to do about it. I'm going to ask about a lost & found tomorrow, and talk to the cleaning staff. I've tried calling my number, but no answer (and I'm sure the battery's dead by now anyway). I'm a little worried about what passwords I might have on the phone, though unless someone is a dedicated identity thief I doubt they could/would do much damage. Also, should I contact T-Mobile? Do I need to cancel my number, or can I keep my number if I end up getting a new phone?

Has anyone dealt with a lost smartphone recently? Any tips for how to deal with it?

Found phone

I found my phone! The cleaning staff told me to ask at the facilities office on the 5th floor, and sure enough it was there. I'm immensely relieved, but also slightly disappointed that I won't have a good reason to buy a Nexus One.