Acrobat cannot open Illustrator files, it can only open those files that were actually saved as PDF files by Illustrator. You may want to ask this question in the Illustrator forum: https://forums.adobe.com/community/illustrator
In general, it's always a good idea to keep backups so that the most you can use is e.g. a days worth of work. I understand that this advice does not help you with this specific problem, but going forward, you may be able to avoid this type of problems.
Karl Heinz Kremer
PDF Acrobatics Without a Net
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