You can add it as a new smart playlist. Go to file/new part playlist.
On the options list click "date added" in the first box, click "in the last" in the second box. then choose the number of days, weeks or months. Make sure match the following rul and live updating is checked
You can only get it back by creating a new Smart Playlist.
From the File menu select FILE > NEW SMART PLAYLIST.
Tick Match All.
From the Drop Down Menus select DATE ADDED then move to the next drop down menu on the right of this and select IS IN THE LAST and then move along to next menu and select 2 WEEKS and then select the + button.
On the next line of menus select MEDIA KIND > IS NOT > PODCAST.
Finally tick Live Updating and be sure to name your Smart Playlist RECENTLY ADDED.