Q: How do you find the serial number of an iPod without the iPod?
A: You can find this information hidden away in an iTunes preference file, provided you still have access to the computer that you were syncing the iPod with.
iTunes actually keeps track of every iPod that you have ever synchronized with it in a file named com.apple.iPod.plist for Mac users, or iPodDevices.xml for Windows users. On a Mac, this preference file is located under Library/Preferences in your home folder, on Windows it’s under a folder named “Local SettingsApplication DataApple ComputeriTunes” within your home preferences folder. Note that this path will vary slightly across different versions of Windows, so you may find that the easiest way to find the file on a Windows platform is to simply perform a search for “iPodDevices.xml.”
On Windows you can simply open this file in a text editor and you should be able to find the serial number listed in a section labelled “Serial Number.”
On a Mac this file will likely be a binary properly list file so you will either need to convert it to XML or use a Property List editor app. If you’ve installed the Mac Developer Tools you should be able to find an app called “Property List Editor” by doing a Spotlight search on your Mac that will be able to open this file for you. Alternatively you can use the Mac Terminal and the “plutil” command to convert this file to a text-based XML format.