Thankfully no! My mother wouldn't ever walk into a room without knocking when I was with my ex, and to a certain degree we were careful to make sure we weren't caught too.
I'm still incredibly glad room service always knocked when we were on holiday - you hear some real horror stories about them just walking into rooms.

I'm sure they thought something odd was going on though (or they were timing it) as they always knocked at just the wrong time...