Thanks. The file contains only zeroes:
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Unfortunately there is no data in the file that can be salvaged. Something has overwritten or otherwise corrupted the file.
When a project is saved, Spine writes the file elsewhere. When that finishes successfully, Spine removes the old file and moves the new one to it's place. That way a crash during saving is unlikely to corrupt the project file. Other disasters can happen though, such as power loss at just the wrong time, bad RAM, bad storage device, malicious software, and other terrible things.
I'm sorry there is no way to recover the file. π