Wow, that has been a while. Was the address you provided them a Cebu address?
If that is, you can tell them to please send another copy to your sponsor this time. Tell them that you are worried that the letter might have been lost due to the Typhoon Haiyan (Yolanda). It's not lying, it could possibly true because so many things were destroyed and misplaced ( even people). Give them your sponsor's address and tell them that you will just ask your sponsor to send you, your LOA via courier.
This is what I would have done. Maybe you should wait for other members to give their opinion about your situation.
In the meantime, since you have your LOA (congrats), start preparing your documents for CIC. ;D ;D ;D