If you haven't emptied your Trash and Downloads isn't in the Trash, then you haven't really deleted it. It sounds like you may have just removed Downloads from the Sidebar and the Dock.
Open a Finder window and go to your user/home folder. Within that folder you should see Downloads. If you do, you can add it back to the Dock just by dragging it in there. (If the Dock is on the bottom of your screen, put Downloads to the left of the Trash but to the right of the faint bar that separates folders from applications in your Dock.)
As for the Sidebar, if Downloads is in your user/home folder: In the Finder, choose Preferences (under the Finder menu). Then under the Sidebar tab, check the box next to Downloads.
Let me know if those suggestions solve your problem....