Try exporting to IDML and opening that. (Don't throw away your original document immediately. Just to be Safe.) It might loosen up some of the grit that accumulates in InDesign files.
If that doesn't work, you can try unzipping the IDML -- just append ".zip" to the file name -- and use a good plain text editor to search through all files for these paragraph style names. At best it'll show you exactly where they were used, or at least you'll know for sure they weren't used anywhere.
Thanks for the response. Two interesting suggestions. The first one didn't change anything. The second, when I changed the idml to .zip it still opens in InDesign and when I force open it with TextEdit, it says it's not a valid file. If I open the indd in text edit, it doesn't really give me any more info. All of my style sheets only appear once, in the style sheet main listing towards the top of the document. Any thoughts? Could be user error...
Changing the extension to .zip should have made your system extract the individual files ... They are all plain text files, in XML format, so you can open them one by one with TextEdit and inspect them.
(Since you are apparently at a Mac, I'd suggest downloading TextWrangler 'cause it allows you to search through multiple files with ease.)
I tried the imdl to zip thing a few different ways but none worked. The TextWrangle app is pretty neat. I'm going to look through it more later and hopefully find what I'm looking for. I'll update this post after I do that. Thanks!
Update: I got the zip thing to work. I zipped it with the built in utility, then had to uncompress it with a different utility (StuffIt). Otherwise it recognized what the file originally was. Then, I used TextWrangler to do the Multi-File Find function. I think I found one place where it is used, story_u635. The xml file doesn't have any text in it, so how do I figure out where that is in my InDesign document? It refers to a table, but is that just xml language, or is that a table in my document?
So far all of you suggestions have been really helpful. Thank you!