I just checked, and that's exactly what happens. I guess this is also a personal preference, and I can see the downside and can imagine that missing a wake up time is worse than a little embarrassment in the theater, but I prefer it the way my phone does it. I'm sure you prefer the iPhone way, and that's cool too.

I'm also fortunate because the buzz from the vibrate IS my alarm sound That's more than enough to wake me up!

Lastly, this is the reason I use an app called Shush!, which turns the ringer/volume back on after a preset time, so I don't have to ever remember it.