Sometimes we sleep. We have even been known to be away from the keybord to bathe (but usually not for longer than 2 minutes once a week ).
I don't know how you automagically did it last time - your details are lacking. iTunes is normally terrible at following you moving things, especially from drive to drive. You either have to let iTunes do the moving (by consolidating to a new location) or you have to disable iTunes managing your media in which case it will follow moving inside a drive but still not between drives.
Despite the new version, iTunes still does not make it easy to split your library between drives. Probably since you only buy your items from iTunes and are never away from a high speed Internet connection it doesn't matter since you can always stream or download items you need from your Match subscription, right?
Small hard drive? Split your iTunes library across multiple volumes - http://www.macyourself.com/2009/04/24/small-hard-drive-split-your-itunes-library -across-multiple-volumes/ - copying media folders to external, then deleting from internal, then adding again.
Splitting & Managing Your iTunes Library - http://machintsandtips.com/i-j-k/itunes/splitting-managing-your-itunes-library/ - using option+drag to override iTunes from copying file to your default media folder.
Dougscripts: Relocates selected files to a folder of your choice - http://dougscripts.com/itunes/scripts/ss.php?sp=relocateselected - replaces "Move Files To Folder"
https://discussions.apple.com/message/10160819#10160819 - Change location of media folder to start putting files on second drive. Note later follow-up post about leaving 'organize media' and 'copy to drive' checked.
TuneSpan: (OS X app) A utility that allows you to distribute the media files in your iTunes Library across multiple drives. - http://tunespan.com/ - https://itunes.apple.com/us/app/tunespan/id528459889?mt=12 - Requirements: OS X 10.6.6 or later, 64-bit processor
Thanks for volunteering to help Limnos!
Your post made me realise i missed out a very important step that i manually did which helped me link my itunes library with podcast located on an external drive. the step was....
after moving the podcast, when i tried to play it from itunes, it would tell me the file is missing and would ask me to locate it. it was around this time that it would as if i wanted to try and locate other missing podcast/itunes u videos of the same collection. that way i would get my library partially linked to an external drive!
im marking ur post as helpful and this one as solved.