You can securely revoke, activate your keys, retrieve or reset the YubiKey ID, AES secret key, etc. from the YMS server if you have client admin rights for the YMS server.
To enable the client admin rights send following information to "yms@yubico.com":
1) 2 consecutive OTPs from one of your YubiKey that you want to use to access the YubiKey Management System to manage your own YubiKeys and client information.
2) Paypal transaction details of YubiKey purchase.
We hope this answers your question.
Feel free to write back to us in case you face any problems.