My entire music collection is gone from Finder
It seems unlikely it would delete them, but I don't know how that app works at all...
...so, assuming Tomahawk has moved the files to its own cache/storage location, you could try using something like EasyFind (freeware) - which can search hidden locations far more easily than Spotlight - to look for either Folders containing the name Tomahawk, or one or two actual music file names.  

Chances are, you find one, you've found them all.

Without Time Machine as a quick revert, moving them back to their original locations may not be so simple - it might be a case of dragging each one back to its correct folder, one at a time.