Do dentists or orthodontists usually order you retainer the exact number as last Invisalign instead of scanning teeth?

I am not happy with my lateral moving past weeks while waiting for a retainer. My dentist removed the brackets from central and laterals up top and ordered my retainer off of that particular number instead taking time to scan my teeth. It was already too loose. Is this normal? Another week since brackets off those laterals are going back like they were ... with the brackets they held better, now one in one out. I want to know ...shouldn't my teeth have been scanned?