Why does iTunes want to assume my iPhone is connected?

Every time I fire up iTunes (latest version), it displays on the left that my iPhone 3GS is connected. But it's not. If I mistakenly click on a playlist under the iPhone instead of under iTunes, it gets all confused trying to find songs that aren't there. Because the silly phone ain't even connected!! Sorry I'm getting exasperated. This has persisted through two version upgrades. HOW do I get iTunes to properly recognize what compatible devices are or are not connected?? Yes it has occasionally displayed my non-connected iPod Classic as well. And YES I am following the proper procedure for disconnecting device after they ARE connected and I'm through with them.