Cannot search Sync folder on external drive?

I use Sync for cloud storage, and it had saved over 200GB of data on my hard drive. I bought a Western Digital 2TB My Passport drive and moved my Sync folder to it. Now I can't search for files - when I do, I get wither a few random results or a large set of results that are not correct (i.e., it's showing me files that do not have the search terms in their file names, or associating files with the wrong file name). I'm really trying to avoid reformatting this drive - it took two days and over half my monthly data allotment to get it synced. Western Digital says it's not their problem. Help?