Perhaps the text you are searching has been converted to outlines. Also check the master page(s).
Look under Type>Find Font. If there are no fonts listed, then your Freelancer has converted all the text to paths. If that is the case, you will either have to rekey it, or make pdfs and use an OCR program to try to read it back to text.
I went to Find Font, and it was able to highlight the text that I can't edit. The font was Arial Bold. This is good, right?
Yes, that means it's not converted to outlines. Without seeing the actual file, I can only suggested exporting the file as IDML and seeing if the problem goes away in the new file.
More than li9kely6 it's either on the master page or locked. Open the Layers panel and expand the layers to see if the frames are locked individually.
Are the text frames locked?
Or are you unknowingly work as part of an InCopy workflow? Go to the Links panel and look for icml files listed there…
If yes, it could be that you could edit the text frames but could probably not do a text search: that means InDesign will do the search, but cannot find anything in the "checked in" stories.
I never used that workflow, but a little test (with InDesign CS5.5) showed, that you can get text frames you can edit with the text tool, but a simple Text or GREP search will NOT find anything. First you have to "check out" the story…
See the following screen grab (my name is part of the contents of that text frame, but Text Search will not find it):