Lost playlist (Auto-updating Apple Playlist)

Please help me recover the original "In my room" playlist!

Yesterday the playlist had 100 songs and I forgot to save the ones I love. Today there are only 65 songs on the playlist. How do I recover the original playlist or find the songs I had heard?

This "in my room" playlist is an Apple created auto-updating playlist which is why the track list changed... Wish I knew that before.