When you create a new wallet and its displays your recovery words. I'm pretty sure its ask you to verify the words before being fully setup!
I had to enter first letter of word 1, second letter of word 5, and so on to confirm that I had recorded the recovery list.
Are you absolutely sure you didn't write it down?
Yes, just checking I had to confirm my phrase. Not sure if it will help jog your memory or even if you used the same ledger. Watch at 6:45 I had to verify my seed words.
WOW.. interesting