Make sure you are looking at your whole Loop library and not just a part of it because you have set up one of the 'limit' filters by accident
For example, in the Loop Browser, make sure you have selected Any in the Time Sig drop down menu... and you have selected Show All in the View Drop down menu
The other filter options are shown here.. under the 'limits' sections about half way down the page..
if this doesn't work...
Rather than using Finder to locate the loops.. try using FindAnyFile for Mac.. (Google for it..)
...and search for a specific loop name or partial name that you know of that should be there and see where that app finds it..
If you find them then it's time to try rebuilding Spotlight's indexes.. (rather than the Loops Browser's Indexes)
If you cannot find the loop files at all then redownload them under the "Download Additional Content" menu option in Logic Pro