I have never seen a fridge that did not have a drip pan. You need one as it is what captures water in the defrost process. Sounds like yours got separated in transit or something. It should not be a big deal for the place you bought it to get one.
you have a drip pan. you just can't see it. it's probably cracked [only leaks certain times]. this will be covered by your warranty from factory[1-year]. it's a bear to change, if you haven't done any, so let them do it.