Did you not receive an email confirming receipt?, if not, I would be slightly concerned. That said, it could be delayed due to the heavy recycling activity for the February avios bonus.

How did you post it? special delivery, recorded or normal post. If the latter, did you keep a confirmation of postage receipt, even if you did, I believe it will only cover up to £32 compensation if it's lost/stolen. You could give them a call on 0800 015 0900 or email at [email protected]