QUIT LOOKING, I FOUND IT!
No replies, but after posting I did more research on OnDrive and I think I fixed it I wasn't aware of the options of having your files only on the cloud, or both on the cloud and my HD. I assumed it was just the latter, which is what I wanted, and the reason I migrated my spreadsheets and related data files to OneDrive in the first place.
It turned out that basically, I was in "FIles on demand" mode on my computers for folder/files I was using. The files were not downloaded until I opened them. Those were the files whose size appeared in parenthesis in DIR. Appa