View thumbnail cache in OS X
thumbnail-cache will be random, it will always have the name com.apple.QuickLook.thumbnailcache. So i think you have already found the right location. 

There you find the index.sqlite file is a SQLite database-file containing two tables: thumbnails and files. 

The files table contains the name, path, file-identifier, and volume-identifier of each file tracked by the database. 

The thumbnails table contains information about each thumbnail, including the file to which it relates (as stored in the files table) and the offset of its data, which is stored as a raw bitmap in the thumbnails.data file. 

may this will solve your question, because all of the Infos are from this Page.