SizzlingCalamariI was able to successfully patch and load the plugin binary, but that is only with -insecure in the launch options. Modifying the binary must have affected how the game sees it as a signed or unsigned plugin.
Well, yeah, signing is basically a hash of the file. If you modified the binary so that it had hacks in it, recognizing it as a signed plugin still would be pretty bad. Every change needs a new signing.
You'll have to wait until the author gets the program resigned if you want to run it secure.
EDIT: Also, I doubt valve will fix it, since it's not their code/project. It's on orange, not them. If he released the source code and someone else compiles it, they would probably sign it, but this isn't their responsibility. At best they'll create their own P-Rec into the game. But a standalone plugin? Nope.