With Keynote open, MacBook skips password requirement after sleep

After a presentation I gave a couple of days ago, I closed my MacBook Pro and put my computer to sleep. I was surprised to find upon opening my computer a few hours later, that no password was required to access everything. With other programs open (Word, InDesign, etc.), if I close my laptop, I must type in my password when I open it up again. Not so with Keynote open. Am I missing something? It seems to me this is a security flaw that needs to be fixed.