When I created a FileVault encrypted partition to install OSX Yosemite, I don't think I created a recovery key. Is it possible to create a recovery key after the fact? How do you do it?
You can access the disk until you forget the password of all users that can unlock the disk. (You might want to create another user for this purpose and store the password safely)
If you did not write the unlock key down nor used icloud storage for it, you have no way to recover or re-create the key.