Based on the event time-line and set process, I think no one is at fault. Also this doesn't seem human error event e.g. Una staff deleted by accident. I have lost the Website setup / data on AWS 2 times and 1 time with other service provider so far, but when I read their agreement/process, then I realize that it was my mistake, as it was my responsibility to keep the backup or select another plan, which does provide the backup option, with additional price.
What I think is, what Una can do to improvise the process is to back up the Data to their own servers, in case the payment is failed or the account is at fault (because sometimes people forget about expired credit cards or other issues or some family obligations or something else and in that event, 10 days are not sufficient to act / decide / respond). When customer comes back, they may reinstate the account data (with penalty / charge / rental depending on how many days they hold the data or keep the refundable deposit, which can be used in such event, so they have enough time to cover the charges or storage).
There is saying which says: "Whatever happened, was for the best. Whatever is happening, is for the best. whatever is meant to happen is for the best. Do not repent the past. Do not worry for the future. The present goes on. You keep working towards your goal and you shall succeed!"
What I mean to say is, imagine if this would have happened when you have had 10000's of accounts down the line? This event has prevented that loss, not just for you but for all of us. And no matter whether you were using UNA or AWS or any Other service, this would have happened there too and I'm an example of this with AWS as well as other small service provider.