Each phone has a unique ID (called the IMEI), used to identify it on whichever network, and so route trafffic (and billing) to it. If you search Google you'll see how some folk can clone these things. The IMEI is hardware specific.
The SIM PIN is something you provide, it's on the SIM card. Put the card in another phone and it goes with it. The SIM card effectively authenticates your account and you as a user (for billing) on a network.
If you're worried about someone flogging your phone on your travels and racking up a bill, remember you simply have to notify your Telco and they'll block the sim from being active..... getting your phone back can be another issue. If your phone is flogged theres 2 things you'd want to do. Cancel the account (stops you being billed) and if possible remotely wipe the device so any other info on it can't get used maliciously. But most likely if its flogged the SIM will be separated from the handset and either both sold individually, or the SIM will be binned. Chasing a stolen handset (through its IMEI) on a foreign, or other network is a time consuming and pretty pointless exercise.
Don't know about encrypted phones, but am guessing if if was a standard handset that someone had encrypted the data on then there will be 2 options.
1 would be some sort of factory master reset, which wipes everything (all user data). This code or key sequence may be readily available on-line or through varoius hack-shops. (Some handset let you do this remotely if you loose your phone) 2nd would be that you can't do anything and its a bin job (or factory service center only) reset.
Either way remember you're talking about a consumer product here, not a hi-tech-high security item. If you have security concerns about losing the device or data then look at how you personally can manage that. Some hardware OS uses systems (like Blackberry) that may enable you to keep the content more secure, but if you're simply travelling the globe then maybe using Google (android) devices where it all backsup to the cloud will be enough. That way if you loose/trash your device, you simply setup your account on another one and you can still access your stuff.
Its all part of the mystery and adventure of travelling