1. Responsibility to have a backup.
2. Responsibility to not screw up live data.
When someone screws up on #2, it inconveniences the person responsible for #1 and potentially loses any data since the last backup. That is the limit of #2's responsibility in this.
If #1 hasn't done his job right, it will come out when someone eventually plays the part of #2 (mistakes happen). Once that happens, the damage from not having a backup is #1's responsibility, not #2's.
In this case, we do not have clear information about who was responsible for #1.