Sounds like he deleted the orders from the "orders" table by manually hacking away at data via phpMyAdmin instead of using the "delete" button in your admin. That has left all kinds of other records out of sync.
You can "retrieve" the deleted orders by restoring those deleted records from the backup you made of the database before you went in and deleted things. You do make regular backups right?
Restoring those specific records will require very careful study of the database backup file to identify the right ones before loading JUST those ones into your database. I STRONGLY recommend you commission that task to someone who knows what they're doing when it comes to database content.

Or, if you want to delete all the other components of those orders, go and hack away in phpMyAdmin and delete the corresponding records from all the other tables that store order details: http://www.zen-cart.com/wiki/index.p...#Order_History


REMEMBER: Manually hacking at raw database data can cause unpredictable results in your store, and if done incorrectly can cause serious data corruption, rendering your store unusable. PROCEED AT YOUR OWN RISK, and ALWAYS make backups before making changes to anything.