You can try to make all items on the operating system visible, with the proviso, you don't attempt to delete, move, or rename any file you don't have any idea what its origin is from or its need for the operating system. To do that, you need the tool called Tinkertool:
http://www.bresink.com/osx/TinkerTool.html
If the files in the trash that are rendered visible are files you created yourself, only then should you desire to delete them. Otherwise, you may render your system inoperable. Check with an authorized service center what may have been the source of the said files that you have no idea their origin, before attempting to delete, move, or rename them.