The command would be useful in the case the backpack gets somehow deleted, especially if the command can do some sort of tab completion too.

The problem I see with that is players won't know UUID of their backpack most probably not even first few characters until they would need it for this command and I am not sure where they could dig it up. Also you could then pretty easily use vanilla command to give yourself backpack with the uuid passed in nbt part.

I was actually thinking of starting to track who crafted what backpack and then add command that would allow players to see all backpacks they crafted, but I still feel that would have very limited use. So I will leave this issue request open for now and decide whether I want to go ahead and add that command.

Released commands in the latest release on CF