Yeah exactly, was anything else missing in your backyard? How long as it been sitting in your backyard? open view yard or fenced off?
its very rare that people go around “prepared” to steal random motorsets from backyards, they knew it was there and snatched it up. They must have arranged a large vehicle to move it… in othe rwords they planned it and knew about it. Depending or how long its been sitting there its more than likely someone you know or dealt with and not someone going to from yard to yard jacking random shit and even them he’d have to come back with others at a later time.