Iphone Icon dissapears in Itunes?

[Rebsola]

I did a search in the forum, so I apologize if this has been already addressed.
When I sync my Iphone everything works fine and than once it is finished syncing the "my I-phone" option dissapears on the left panel of I-tunes? (although it is still charging) If I download music or whatever I have to dissconnect and plug back in. Is this some sort of option I have chosen? It didn't used to do this. It's not a jailbroken phone.

thanks