The .big file is the sounds for Xpand2! synth which also is in your Avid Account.
If you are refering to the Big Fish Loops library it was a few years ago Avid removed those and ended the collaboration with Big Fish. No one knows why as far as I am aware so you can stop looking for them since those won't be found anywhere anymore. Also there are soo much better loops and sounds to find for free as the Big Fish stuff felt old as hell even a few years ago and since they weren't updated I don't think many users miss those any longer
Sorry to be the barer of those news but there are soo many free loops all over the web that its actually impossible to keep track of all those sites
Google is your best friend for that escapade.