Back in the day, when people had such things, we would tape various words on our reel to reel tape deck and play the tape backwards. The final W in words such as cow and shadow definitely sounded like a normal initial W when the word was played backwards. You don't hear it when the word is coming at you in its usual way because you're not listening for it. And even if you are listening for it you don't know how to hear it. But it's there nonetheless.

Zwoan wodash uth.