I've gone through all the steps to restore backed up podcasts, and I actually have all of them in a folder next to the iTunes Media folder.
Each time I reimport the podcasts, iTunes copies the podcasts faithfully back into the iTunes Media folder.
Once the copy is complete, I check the settings and make sure auto download is off, do not auto delete, etc.
I can line up the iTunes window and the finder folder next to each other, and when I hit refresh (as there are new podcasts every week) certain podcasts magically diappear from the finder window, and the cloud / arrow icon appears next to the episode in iTunes.
I have just done thr same, but unchecked sync podcast subscriptions in the preferences - store section, hit refresh and the episodes did not delete. Hurrah.
However, that raises another question: can I still download the latest episodes by manually refreshing the podcasts? Let me try... I have just deleted from the folder, and iTunes the latest of one of the podcasts, and when I clicked refresh, iTunes downloaded the file right back again, and didn't delete it when refreshed again.
It seems we have a winner - if you set everything to manual, ie. do not auto delete, uncheck sync podcast subscriptions, automatically download - off, and keep - all, the deletey thing doesn't happen (I've tried it a couple of times now, and it seems to be OK...).
Thanks to all who contributed to the solution - it's been bugging me since the update went off - especially turingtest2...
Cheers,