Theory
The restore worked and took four days
A restore can return all the data and still come too late. Time, sequence, and hidden dependencies often cause the loss. Restore order, recovery credentials, network capacity, and staff availability do not appear in a backup report, but all of them appear in a timed drill.
Common causes
Claim: observation
Restore order was never established, so systems came back in an order their dependencies did not permit. Credentials needed for recovery lived in the system being recovered. Network capacity made the transfer time dominate everything else. The recovery runbook assumed staff who were unavailable.
None of these appear in a backup report. All of them appear in a timed drill.