The reseller (or the providers staff member) is not able to view the content of the previous versions of the store layout templates, therefore no way to restore the templates' previous versions.
The reason is a privilege
AUDIT missing in the staff member's role.
If this is a providers staff member - add the privilege to the staff members role or create a new role with this privilege and attach it to the user.
If this is a resellers staff member - check if the reseller has the privilege AUDIT delegated:
resellers subscription -> resellers plan -> resellers template > Privileges tab
if there is no privilege AUDIT, add it with
Attach New Privilege button;
synchronize the reseller with an option "Update Reseller Roles/Privileges";
the privilege will be automatically attached to the "Full Access" role, if required it can be added to other resellers roles.