How much does it cost to replace a stolen iPhone 5 that has insurance?

I think my iPhone may have been stolen, reason I'm not 100% sure is because I may have just left it at home before I went back to school to work (I work in DeKalb, but home is an hour and a half away in Chicago). I don't want to report it stolen until I'm 100% sure it can't be found. But other than that, has anyone had any experience with putting in a claim with AT&T for their stolen iPhone 5? How much will it cost to replace it is more of my problem. I don't want to get stuck paying $500-$600 for a stolen phone, that just doesn't seem fair. I'd really love to know this before noon tomorrow.

If you have insurance, all you have to pay is the deductible, so you need to find out how much is the deductible. But I recommend that you go to icloud.com and sign in with your Apple ID, and from here use "Find My iPhone", to track the your iDevice.