Warped blade are not as uncommon as you may think. The heat treating process does it. The thinner the steel, the more likely it will warp. I'm pretty sure razors were either only partially ground or not ground at all before the heat process took place. After they were tempered, a different process, then they were ground. No way could they have been ground to their normal thin profile and then heat treated.
I have knifemaker friends who do their folders this way to ensure the blades do not warp. Warped blades can be fixed. Use a big vise.
Put the blade parallel to the top of the jaws near the surface. Vertically insert one wood dowel on each "low" side of the blade at the spine. Then insert a vertical dowel on the opposide side of the blade at the tangent of the "high" side on the spine.
Crank the vise shut until you go a little past the curvature of the bend. Practice on some junkers first. Do a little at a time and keep checking to see if the blade is straight.
Tip: Tape the dowels in place on the blade because you will need 5 hands otherwise to get them where they need to go.