The same happened to us. If you were using the Free version of MoodleCloud, they have a 60 day inactivity policy and after 60 days (and at least one notification - that we missed), they delete the site. Here is the message I received from support - and in a follow up i learned that after 90 days there is no chance of recovery - so, if you are willing / able to pay $100 AUD, then i would move quickly if you are in the 60-90 day window:
"Sorry to hear you have lost your site, under our free site retention policy, if your Moodle for Free site has been inactive for more than 60 days, it is removed in order to maintain a vibrant and active system for all users. We do send a reminder email message before the site is removed.
Your site - xxxx.moodlecloud.com was deleted on the 9 October 2019. A warning email about your inactivity on your site was sent to your email address on the 25 September 2019.
To get the site back online, our technical team are able to restore your site data but as this is performed by our technical team there is a fee of $100.00 AUD to go ahead with the site restore. Also please note that to comply with our GDPR
policies, as you are no longer as a customer, you will need to reply to this email for us to go ahead with the site restore within 14 days of the site deletion or your site will be deleted from our systems."