It seems they did a backup AFTER the errors, so it only showed 700 members, 4300 lost. Two guys who have helped with my site, did have backups from July 04, so they saved about 3000 total.
The other 2000, they created a script that showed up the missing as "LostUser100433" (example). So, those people who were lost could re-register and then merge their username and old usernumber.
Headache, big time.