Sounds like toast to me.
Chalk it up to a valuable lesson and move on. You’ll spend way more time trying to recover this corrupt file than it will take to recreate it.
Please email your InDesign file to email@example.com and I will take a look at the document.
If the file is larger than 10 Mb, you can zip (and password protect) the file and upload to Creative Cloud account (or Dropbox) and send us the document link.
I have a similar problem and am receiving the same message, "Cannot open file "". Adobe Indesign may not support the file format, a plug-in that supports the file format may be missing, or the file may be open in another application." However, now the file is missing.
I am using ID CC 2017 and was performing a "Save As" with this file open in InDesign to try and reduce the size of the file (original size @619MB).
I am using Windows 7 Professional. You can see the file in the background of the attached snippet. The file is called CapabilitiesCompleteDec2016.indd. But every time I try to open the file I get the same error message.
This is the only copy of this file. Please tell me there is a way to recover the file.
Thank you very much.