How to determine original location of file that is currently in the Trash?
Data containing a file's original location before being placed in the Trash is keep in the .DS_Store file in the ~/.Trash folder.

Since the trash folder is hidden it can not normally be found using the finder application.  The easiest way to find this file is by using the Terminal and entering the following commands.

$cd ~/.Trash
$open -e .DS_Store


This will open the file in TextEdit.  From there you should be able to quickly search for the file by its name and its original path.

Its seems that files in .DS_Store follow the pattern of:

FILE_NAME ptbLustr ORIGINAL_PATH_TO_FILE


Note spaces are added just for readability.