I think you'll need to call support on this to see if it can be restored/imported somehow. It's annoying, but prioritize doing this now before working on more returns in case anything gets overwritten. I hope they can bring it back for you.  Agree, I'd lose my mind too.

If you have to repopulate it, figure out a system.  I'd buy and hook up an additional monitor, have PY Lacerte on another screen and get really efficient at copy-paste.  Hire an admin to work ahead of you and populate items in the returns you'll be going to next (my admin might want more hours, TBD, so lmk if you need/want help).  Just a few ideas that I really hope you don't need.