Podcast subscriptions disappearing

This is the second time this has happened now and I'm getting massively ****** off.

I start up iTunes, and the podcast link has disappeared from the sidebar, all my music is 'missing', so I get iTunes to search for media. It finds my music and podcasts I have but if I am subscribed to a podcast and did not have any podcasts saved on my computer then it no longer shows up and I have to subscribe to it again.

Why does this keep happening? I can't see the point in subscribing to podcasts through iTunes if it keeps chucking them every few weeks