Purchased Songs Missing from a Playlist, But Still in Library

I have a playlist called “Pool.”  Two weeks ago, it contained 152 songs.  Today, it has only 32. The 132 missing songs were all purchased and downloaded from the iTunes Store.  The 32 remaining songs were all burned from CDs.  Thankfully, all of the “missing” purchased songs are still in the Library. From time to time, I also save to PDF select playlists, including “Pool” so I have an electronic copy of the 152-song list. Also, I am not a subscriber to Music or iTunes match, so this is not a iCloud problem.

The iPod touch which was manually synced about two weeks ago was not affected; it contains all 152 songs in the playlist “Pool.” 

Obviously, I would like to restore “Pool,” but you can imagine how tedious and time consuming this will be to restore the playlist by moving each song, one-by-one.  As an experiment, I tried this with one or two songs and was met with this message: “Adding purchases to playlists will download a copy to your computer.” I have been using iTunes for over twenty years and never encountered this message before.  More importantly, the screen alert makes absolutely no sense to me since the purchased songs have already been downloaded.  Fearing adding unwanted duplicates, I hit the cancel button.

So, my question is this: short of lint picking 132 missing songs is there an easier way to restore this playlist? Is it possible, for example, to reverse sync the iPod touch to restore its intact playlist to the Mac?  (a pipe dream, I know). If I do the tedious lint picking, will I be creating duplicates in the library?  What about Time Machine? My understanding is that Time Machine is no help since it does not back up playlists or am I wrong about this?  Any other options that I have missed other than going into the Library which at my age (78) would be a very dangerous choice?

Finally, anybody care to speculate how this could have happened.  All theories welcome. I am running Mac OS 10.15.7 on a 2018 Mac Mini.