The linked twitter thread explicitly mentions data loss:

> Hi Andrea. It is confirmed we have lost data and we are terribly sorry for that. However, please note that what happenend[sp] could happen to any web host.

Customers that were forced to migrate to a different webhost had to restore from whatever backups they had, and they lost data for sure. Even if Gandi ultimately recovered everything (and it's not completely clear if they did) at that point the customer data/databases have already been forked so it's too late.