I always drained mine down past the skimmer and plugged the lines and drained those. A plain ol' tarp is all you need just to keep the crud out - that's the only purpose it serves. Let it droop down and lay on top of the water. You can keep it from blowing away with bleach bottles filled with water and tied to the eyelets and hanging down the sides of the pool.

Solar covers only last a few years before they start to break down and fill your skimmer and filter with bits of plastic so its a good possibility that's what happened rather than him taking it. Buy a new one in the spring.