@kristinmattei22 I moved your post over to this existing thread: Content disappears when Premium session ends
To clarify, it looks like your account is currently set up with Pandora Plus. Customized playlists (including your My Thumbs Up playlist) are only an option when upgrading to Pandora Premium.
I had our support team take a look at your account, and it appears you have been enabling free sessions of Pandora Premium by watching an ad.
This is what was allowing you to access your My Thumbs Up playlist.
When these free sessions of Pandora Premium end, your account reverts back to the free service, and you no longer have access to that on-demand content.
That would confirm why that content was no longer showing in your collection at the end of those Premium sessions.
For a complete explanation of how Pandora Premium sessions work, check out the accepted solution to this thread.
Hope this helps!
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