Where is the offline copy of my onedrive synced Onenote file?

I have moved from Windows 7 and OneNote 2010 to Windows 8.1 and OneNote 2013. I backuped my OneNote book to a external drive and then opend it on Windows 8.1 again and (because i wanted to sync my Notebook with my Windows Phone 8.1 OneNote) I made it stored in my OneDrive as suggested by OneNote. This works pretty fine, everything is sycned properly and so on.

But I do not see where the local backup of my OneNote is stored on the PC? And this confuses me, as all my OneDrive files are made offline available on my PC. Under C:\users\<user>\Documents\OneNote\ there is no OneNote (or related) file. Under C:\users\<user>\Documents\OneDrive\Documents\ there is a shortcut/link to (apparently) my OneNote file on Onedrive. So nowhere on my PC I can find my 1.3GB OneNote file, although it is made offline available.

My final question after this long introduction: Where is my OneNote file stored on my PC?

The OneNote offline cache is stored in C:\Users\<user>\AppData\Local\Microsoft\Onenote a hidden file.