I’m sorry you’ve had this issue. Please consider using source control in order to guard and protect your hard-earned work.
Personally I use git because it is free and there are tons of tutorials out there to help you set it up.
Here’s how I use git in one of my games, Jetpack Kurt:
Using fine-grained source control as you work to refine your engineering:
Share/Sharing source code between projects:
For this issue, here is how to solve:
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get your project into source control NOW
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make a fresh HDRP project the same way you did originally
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copy the files from the new empty project to your current project
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keep using source control to avoid unpleasant future surprises like this.