If the original tenant does not exist, no the files are lost. If it does, you should still be able to navigate to the tenant (login using a SharePoint admin or Global admin to the old tenant, https://tenantName.sharepoint.com/personal/<OneDrive_Site>.
If the ODfB sites have been deleted and it is within 30 days, you can recover them by using Get-SPODeletedSite -IncludeOnlyPersonalSites (https://learn.microsoft.com/en-us/powershell/module/sharepoint-online/get-spodeletedsite?view=sharepoint-ps) and restore using Restore-SPODeletedSite -Identity <site_guid> (https://learn.microsoft.com/en-us/powershell/module/sharepoint-online/restore-spodeletedsite?view=sharepoint-ps).