This reminds me of what happened to the financial services Cantor Fitzgerald after 9/11, just replacing a system with hundreds of lost employees:
https://www.nytimes.com/2014/11/19/magazine/the-secret-life-...
https://www.nytimes.com/2014/11/19/magazine/the-secret-life-...
They had backups and were able to recover data and systems.
By the time I got there, they were somewhat functional.
The biggest problems were the lack of knowledgeable personnel, not lost data or systems.
I was there as a consultant and didn't know anyone there when I went.
I won't provide any details out of respect for those fine people, but the grief was so thick, you could have cut it with a knife. As I said, I didn't know anyone who was there (or wasn't there) but after a day, I wanted to cry.