This outage may have been technically out of uCools control and no fault of their own, but it was their customers that were affected by this outage. If you are prepared to allow another organization to hold your reputation in their hands, e.g. using a cloud service provider, you are at the mercy of that third parties indiscretion's and failures. As you are the employer of the contractor you are responsible for their actions in regard to your services, therefore you are obliged to compensate your customers for the losses that they have suffered and we have all put a lot into this game, even those that have just invested time.
As for your Facebook notifications, I don't think that they were in any way adequate. Saying that the servers will be back shortly for nearly 12 hours is not putting your customers best interests at heart. Working in the IT industry and having gone through something similar I know that would have been the information that the cloud service provider give to uCool, but it does not make it adequate, nor acceptable. It would be best for all parties if the timeframe given was appropriate and not just a stab in the dark, hope for the best timeframe as give to us.