It seems that a year before Apollo 13 during a runup to Apollo 10, they simulated a similar problem. For grins, they gave the LEM controllers the problem of powering the LEM with a double fuel cell failure. They couldn't figure it out, and the (simulated) astronauts died.
To power the LEM you need power from the Command Module and ultimately from the Command Service Module. That allows power to relays that give the LEM its power. Without power to those relays, you can't turn on any of the LEM equipment. There are workarounds, but the controllers couldn't figure them out in real time.
Afterwards, NASA told the controllers to ignore the problem as a double fuel cell failure would never happen. However, the controllers were not deterred and worked on a procedure to accomplish the switch-over. Their procedure took about 30 minutes, and they put it on the shelf. It wasn't an official NASA procedure.
When Apollo 13 lost both fuel cells, it was that procedure the LEM controllers pulled off the shelf. They also managed to cut the checklist down to 15 minutes.
Without that previous work, the Apollo 13 astronauts would have died. Those NASA Apollo controllers were the "Right Stuff!"