Your trash directory is most likely at:
/home/$USER/.local/share/Trash
If you deleted something as root (e.g. deleted a file using Nautilus invoked via gksu), it is at:
/root/.local/share/Trash
(In general, according to Freedesktop.org specifications[1][2], the "home trash" directory is at $XDG_DATA_HOME/Trash, and $XDG_DATA_HOME in turn defaults to $HOME/.local/share.)
To see .local in your home folder using the file manager, select Show Hidden Files from the View menu or just type Ctrl+H.
The Trash directory is first created when a user deletes a file. Within Trash there are three subdirectories:
files, where the deleted files are stored until the trash is emptied
info, which stores information on where the files once were and when they were deleted
expunged, to which files are briefly moved when the trash is emptied (but may contain some owned by other users from directories you deleted).
Note that using the rm command in a terminal or the Shift+Delete key combination in the file manager will permanently delete your file instead of moving it to the trash.