While what we have of the soundtrack is great, it's really too bad that we are missing the credits song from the end of Call of Pripyat. While it is a vocal track from another band/composer, I was really hoping the OST would include that song in FLAC.

Probably not included due to possible copyright issues.

The track is "Firelake - Live To Forget"

It is possible to extract the .ogg file from the files though.

How would one do that exactly?

I think I found what the track itself is. It's "Firelake - Live To Forget". Firelake made several tracks for S.T.A.L.K.E.R. games.

If you really want to extract the file, you'll need to extract all the files. Check Step 1 of this guide
http://www.moddb.com/mods/call-of-pripyat-redux/tutorials/creating-your-first-stalker-call-of-pripyat-mod

The track will be in sound/music folder named credits.ogg. However, it still has the second half of the credits (which is the menu music.)