When you get the chance, take it to a LV store in your area. They will perform a quick free authentication. They really stand behind their product and will go the extra mile to get to the bottom of this. You will not get in trouble if it's fake, but you will know beyond the shadow of a doubt if it is real.
If you are not near a store, try emailing them detailed pictures. I have not personally tried this, but given their high standard of customer service it should be possible.
If it's not real, take it back and complain until they give a refund. If they don't honor their guaranteed authentic policy and you don't care to do business with them again, tell them you will inform the LV store or police and be on your way. They may change their tune.
Some of the fakes are really good. I have a real LV wallet (100% authenticated) that I carry as a kind of acid test for the thrift store stuff. Some of it - even otherwise obvious fakes - come close in the look and feel in the leather department.
Why would anyone offer genuine LV at a discount? Think about it. The stuff's worth it's weight in gold and everyone knows it.
Maybe you got lucky, but the only way to be sure is to contact LV.
I do wish you luck; let us know what you find out