The registrar does not own the domain, you will never lose its domain if you are the registrant. In the worst case, Verisign or ICANN comes into play.
It also depends on whether you buy your domain from a seller or a real registrar. If the seller suddenly shuts down, all you have to do is contact the domain registrar and access your domain from the company panel. On the other hand, if a real domain registrar, not a vendor, closes the business, ICANN will have control over the domain and move the domain to a new registrar. You can then renew the domain. It is always important to have real WHOIS information in your domain because in such a situation you can use your domain easily.
However, if you have used any privacy protection and the registrar masks you as the owner, you may need to create your purchase receipt for the domain, even if there is an email from the previous registrar.