A client had NOL's in 2018 & 2019. We want to carry them back under CARES, but the client is unable to get a copy of his return for the 5th preceding year. Has anyone tried to carry back to 3rd or 4th preceding year, skipping the 5th?

I am trying to recreate his 2017 tax return to do an amendment to claim the NOL. The entire NOL will be absorbed that year. I just don't see how its possible to carry the loss back to the 5th preceding year in this situation. 

Any insight is appreciated!