I’m not a lawyer, but I think this would be on archivetopia. I think the question would be whether healthcorp had taken reasonable care to preserve these records, or had been negligent by leaving them entirely in the hands of archivetopia. It seems to me that the former would be the case, and that archivetopia has failed to appropriately safeguard those files, if a random employee can delete them without any procedures in place to prevent that or to keep additional backups.

Obviously there are multiple points of failure here - any one out of healthcorp, archivetopia, or the employee could have acted differently to prevent this. But if healthcorp had a reasonable expectation that handing these documents over to archivetopia would meet their obligations to preserve them, they should be in the clear - just as they would be if their document warehouse met all health and safety regulations but somehow burned down anyway. In both cases, they did what they could but events beyond their control resulted in data loss. In both cases, there is still a question about reasonable care: Did their warehouse meet all safety requirements? Did they have good reason to believe that these documents would be safe with archivetopia? If the answer to those questions is no, they are still at fault. If yes, they are in the clear.

On top of this, archivetopia is certainly at fault (multiple parties may be in the wrong here). And of course, the employee is at fault, although I don’t know if they’d be legally culpable or if it would be an internal matter.

Not a conclusive answer, but I hope this helps to clarify some of the considerations involved.