I'm posting this in case anyone else struggles with AJAX reading in a local text file.
If your text file has carriage returns in it, and you write to an array using tokenat, ajax.lastdata, etc, those carriage returns will be written to the array's last item of each row. When viewing the array in the debug window, you won't see it. When trying to use those elements to match up values in other objects' instance variables, you won't get a match. It took me 2+ days of troubleshooting the array to figure out that was the problem.
Again, only posting this to hopefully avoid several days of headaches for the next person coming across this.