Was it a Mac? I'm sure MacBooks have the ability to be tracked if the owner allowed it. I have a MacBook pro and the guest account allows a thief to login and I can track them through the guest account.
I didn't realize that Find My Mac works with the guest user under FileVault 2 (full disk encryption built into OS X — the guest user boots into a unencrypted partition that only runs Safari).
Source: Glenn Fleishman http://www.macworld.com/article/1163387/can_filevault_2_and_...