I can see in PDF that the last time I filed a tax return for these taxpayers was 2020. I haven't used anything besides PTO. But when I look back at my PTO for 2020 and before, I cannot find this taxpayer at all. Not for any prior years that I can see copies I prepared and submitted. They seem to be gone. 

Any idea what could have happened and where I can find them.

Thanks for the previous answers btw.