Hello Ayaz,
I am sad to hear on the experience that you have gone through, I totally understand how important this is for you to recovery your data. As per your description, you have purchased from a third party online store. Note that, it is always suggested to get a license or subscription directly from us or you may follow this article on how to safely purchase online or in person: How To Tell - Shop (microsoft.com).
Since you have mentioned that the website emailed you an account, which ends with @hihz.onmicrosoft.com it is a business account, which is not meant for consumer. What happened here is that if someone who has a business subscription, they can create an account (which was the same scenario as yours) and assign subscription which will allow you to have a Microsoft 365 Desktop apps and storage. But on any time given, they will be able to delete or remove that account as they have control over it.
Note that legit retail store does not use this kind of transaction, they will provide you a specific QR or redemption key to redeem your products, for example if you have bought a subscription you will be then given a redemption key and after redeeming it, you will be able to see it directly on your personal account dashboard: https://account.microsoft.com/services.
What I highly suggest report this incident: How To Tell - Counterfeit Software Report (microsoft.com).
I hope this information helps.
Best regards,
Arquel C.
Microsoft Moderator