I'd tell HR the reason you think you're being fired and why it's wrong. Be very specific about it (name the project, circumstances, dates if possible). Try not be angry. Be as reasonable and fair-minded as possible but don't sell yourself short. Then go out for a nice dinner, sleep in late, and find more interesting work.
If you stay in the industry, you'll probably run across your old colleagues at other companies. And if you want to work for that company again, you can check back in a year or so. That manager will probably be gone.
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I'd tell HR the reason you think you're being fired and why it's wrong. Be very specific about it (name the project, circumstances, dates if possible). Try not be angry. Be as reasonable and fair-minded as possible but don't sell yourself short. Then go out for a nice dinner, sleep in late, and find more interesting work.
If you stay in the industry, you'll probably run across your old colleagues at other companies. And if you want to work for that company again, you can check back in a year or so. That manager will probably be gone.