iTunes doesn't show some playlists for sync with iPhone ...

I've got a few smart playlists.
The annoying thing now is that some of them do not show up under "my iphone" / Music / Playlists.
So I can't sync them to my iPhone ;-(

I used to have this smart playlist in the iPhone section of iTunes - but I can't remember when it disappeared.

For instance, I've got a smart playlist that contains some of the latest episodes of some podcasts.
It is populated fine, but it does not show up in the playlists for sync with my iPhone.

Another smart playlist (which I call "random pop") contains some music from my music collection.
This one does show up in the iPhone section of iTunes ...

BTW, just in case you wonder why I have this smart playlist containing some episodes of the podcasts: first, there are some episodes that I don't care for on my iPhone; second, with this little trick I can jump by a simple double-click to the next episode, no matter which podcast it belongs to, while listening to my iPhone.

Any insights, tips, and suggestions will be highly appreciated!

Best regards,
Gabriel.