I would hold the health-care provider responsible. Use of surge protectors would eliminate destruction of computer records.
Btw -- I was in a hospital when it lost power. However, immediately the generator kicked in to power the most important machines and enough light to see.
I suspect it would be for a court to decide. Was a backup copy legally required? If so, who didn't make or keep it. Was power surge protection on the computer?
There are a myriad of issues here, but the basic will boil down to what backup and other protective devices were legally required, and who was responsible for keeping them current and working.
If none were legally required, then the next issue is the reasonable man issue, and I wouldn't want to get into that type of negligence argument.
In addition to surge protectors and generators, there are "uninterrupted power supply" (UPS) devices that any thinking administrator would have on all servers and computers.
But most important, there are companies whose sole business is to provide data back-up services for other companies and agencies. Any large or small company who doesn't contract with one of these is not doing right by their clients/customers or themselves, IMO!!