I have access to the database. I used a program called ApexSQL Search to search for particular strings (the outputted text) in every field of every table in the DB, and nothing came up. Not even the titles of the articles are in there. Heres where it gets really weird: I decided to download the whole site to my computer with FTP, then I ran:
grep -l -i 'TEXT IM LOOKING FOR' /path/to/site/*/*.*
and I made sure it scanned every single subdirectory (i.e. I ran it on /path/to/site/*/*/*.* and /path/to/site/*/*/*/*.*) etc. Bizarrely enough, I couldn't find the articles. I could find some of the article titles stored in these .resource files for some reason, but the articles themselves where nowhere to be found.
The site is made with DotNetNuke CMS (which is a monstrosity of a CMS), and the module which displays the articles is called XMod. There are at least 2,000 of these articles, if they are not stored in some kinda text files (i.e. XML) on the server, then where else could they be stored? I used TamperData to read the headers and I didn't see any GET requests sent to an external site.
I got what I needed from this site another way, but I still would like to know how to easily find the source of text outputted by a web page. For example if the site gets the data from a MySQL database, or an XML file etc.