Wont work, the plastic already has developed a memory your best bet is just To return it or send it to PMG for a reholder.
Will the note be damaged if I do not reholder? This note is not expensive. The seller is willing to give me a partial refund and I can keep the note. I'm deciding.
The bottom line, and the easiest thing to do is just send it back to PMG, just Get the job done right.
The bend occurs from improper storage and/or shipping. You could try to put the sleeve in a book and then put something heavy on the book. Not sure if that will get the bend out entirely but it should help straighten it out some.
Usually how this occurs, is air bubbles get in to the process and cause the holder to become out of wack and not flat.