Does T-mobile iphone comes without a SIM?

Hey just curious if iphones from t-mobile come with out a sim card like other carriers. Sprint for example. Also if i lost my iphone (with no sim) can the person who found it be able to use it?

Sprint is a CDMA carrier, which doesn't use SIM cards that's why they don't come with phones from them.
T-Mobile is a GSM carrier which does use them so it will be included & is necessary.

The person that phone it could use it if he/she also has a T-Mobile SIM and/or if they got it unlocked.

FYI: with iOS 7 installed they would also need the Apple ID of the original owner, essentially it would be useless until then