Loss of annotation in pdf files despite autosave

[Nigel35498996s04p]

Using Adobe Acrobat reader. My PC closed down unexpectedly from sleep mode with 2 pdf files open. Both were set to autosave every 5 minutes and filed in OneDrive. On reopening, all my annotated comments had been lost and I was back to the original file. I am unable to find where temp files are stored, nor see any means to recover the annotated files. 

[Vidya32600283qe20]

I'm having the exact same issue. Acrobat seems to have crashed, and autosave is enabled every 5 minutes, but when I reopened Acrobat, my document and annotations weren't restored, nor can I "reopen PDFs from last session." Help!