Q: random items missing from iTunes

My iTunes library resides on an external hard drive, and I wanted to reformat it from FAT32 to Mac OS Extended. I moved the entire contents to another HD, reformatted, then moved everything back. I started iTunes and all items had an exclamation point next to them (original file could not be found). I checked iTunes>Preferences>Advanced and was surprised to see that iTunes Media Folder Location was still set to the original location on the MacBook's HD, since I've been using the external for a few months now. In any case, I changed the folder location to the iTunes folder on the external and that mostly fixed the problem with the exclamation points. There were still certain songs that couldn't be found. I chose one, clicked Locate and found it on the external. iTunes then very helpfully found 127 other items based on that location. However, there are still 149 items that can't be found, and they don't seem to be on any of my HDs. Some of them were purchased from iTunes, some were ripped from CD and some were free tracks found on various artist/label sites. Where could they have disappeared to?