If I can remember it right...
When I press the sleep button (Fn + F2 here) multiple times, nearly 'at once', it goes into sleep; when I wake it up, it goes again in sleep in the amount of times I pressed the sleep button....
Maybe you pressed the button a little longer, and maybe is your keyboard repetition really fast

Don't know for sure; if what I remember is OK, and my thoughts are a little OK, maybe that could be the reason -- however, it can be something else too of course