OK, so I get a 'check engine oil level' message, and run to my hood and check the dip stick - it's completely dry! No oil on it what so ever. Then, I break out half a quart of oil (I had just added some about two weeks ago, and this seemed like a normal dose) and dump it in. I let it sit for a little while, start the engine, shut it off, and recheck the dip stick - still dry. I know for a fact that I have oil in my car, but I lack knowledge of its location. I've been driving with it, and everything is normal, what could be the cause of the dry dip stick?