If the account password is changed using the client, then you do not need the recovery key! The client will simply encrypt the data with the new password and upload that. Everything is fine.
If however you reset your password on the website, then you will need your recovery key. If you did that without knowing your recovery key (which you do need to confirm you have to reset your password) then you cannot get your data back.
It is vitally important that you do keep your recovery key safe and private while still accessible to yourself, in case you do forget your account password and have to reset it. Without your recovery key it is not possible to decrypt your data after resetting your account password.
