I just noticed this too
Suddenly (it used to be just fine), the Navigator panel doesn't list all of my sidebar items any longer. Interestingly, some do show, but the majority don't. Interestingly, on my desktop the sidebar items show up just fine and it has a similar configuration; same OS (10.10.5) and PM versions (17146), and similar siderbar items. I have tried turning the option “show finder sidebar items in navigator” off and on (with restarts of PM in between), to “reset” things, but the result is the same: OK on desktop, missing items on the laptop.
I'm not sure what was changed to make the sidebar items on the laptop disappear, but now I can't get them back. Weird…
Perhaps there is a simple fix to this…
Update: I just removed one of my sidebar items and then re-added it. Now it shows up again in PM too
Hopefully this will lead you to the cause of the missing items?
Cheers,
Hayo