How to restore PSD file accidentally flattened

Hello,

I have saved the PSD file to PDF for print and unchecked the "Prevent from photoshop editing capabilities"

and when I saved it the file turned from PSD to PDF while it was open in the Photoshop. I closed the Photoshop and re-opend the PSD file and now it's flatten.

How can I reverse it? restore it?

I checked the file for older versions - there is none.

Thank you.