Lost all my ipod touch music, playlists and podcasts

This is a potential risk to using iTunes.

You have to tell iTunes in Preferences not to synchronise tracks between player and computer when connecting.

Also your iPod is only allowed to work with one computer (two if one is a Mac and the other a PC) due to Apple's restrictive agreements with its partners in the music biz and I think this can lead to problems such as you describe.

It's a situation you can only avoid easily by choosing another brand of player next time.