UPDATE 2: Still waiting to receive two missing bitcoins that were purchased on December 11 and promised delivery for December 17. I mentioned the issue to them days ago and it's still hasn't even been acknowledged. Sent them a message this morning and again right now.

Coinbase has been kind enough to resolve the issue with 10 bitcoins being delivered nearly a week late. But I'm not sure why 2 bitcoins disappeared from my account and they have yet to acknowledge the issue.