My current understanding is that the files were imported into Discourse, but went missing somewhere along the way.
I had asked about extensions way back when and had included all the ones I needed:
EXTRA_AUTHORIZED_EXTENSIONS = ["bin", "bmp", "doc", "docx", "gif", "htm", "ico", "jpeg", "jpg", "json", "pdf", "png", "ppsx", "ppt", "pptx", "txt", "xls", "xlsx", "zip"]
It’s not just spreadsheets. I just checked more thoroughly and every file except for images seems to be missing. 
For good measure, I ran rake posts:rebake as that helped with some images woes I had in the past. But no joy.
The files are included in /var/www/discourse/public/uploads/default/original/1X.
I was able to cross-reference a topic in Discourse with Ning.
This code:
<li>
<a>AMICAL 2014 Members Council Meeting - Minutes</a> (14 May 2014)</li>
Should be linking to a file called:
- Ning:
AMICAL2014MembersCouncilMinutes_distmembers.pdf - Discourse:
0baa9dd232fe29c1b7cb53376b0d2feda905e091.pdf
Does this help me at all?