There is a post on MobiPocket's Forum:
TIP - Make own index of ebooks which explains how to extract the title from the file. Alternatively, if you open the (mobi) file with an editor the title and author is usually visible as plain text. Note that there is also a "Database name" which is at the very start of the file.
On the iLiad, mobi (BOOKMOBI) files are treated differently to AportisDoc (TEXtREAd) files, probably because the latter don't have an easily extractable author and title. Note that a BOOKMOBI file can have the extension .prc, but I have not seen a TEXtREAd file with a .mobi extension.
This won't solve your problem, but may narrow it down to a subset of .prc and/or .mobi files.