A good long while back, when OSX introduced Mission Control instead of Spaces, it would migrate across any shortcut keys you’d applied to different spaces. In my case I used 4 single row spaces side by side and switched between them using Alt+1-4. I also used a key re-mapper to rebind # (as this is usually Alt+3). Recently the re-mapper has stopped working correctly and so I decided to rebind the shortcuts to Ctrl+1-4.
But where the hell did OSX these old shortcuts to?
If you go to System Preferences > Mission Control there are no mention of shortcuts. Turns out when OSX upgraded this function, it would carry across any of these shortcuts and dump them into System Preferences > Keyboard > Keyboard Shortcuts > Mission Control. So head over there and update your shortcut keys if need be.
You can also create your own in Keyboard Shortcuts > All Applications, very handy if you’re regularly repeating certain task in other apps.
BTW I’ve not yet upgraded to Mavericks (my standard response for major updates is to wait until major projects are finished before updating in-case of issues) so I don’t know if this stays the same in Mavericks.