God answers prayers, even the silent ones that you are not so serious about and you just uttered them out. God gives hear to it just to make you aware that He listens and He heard you. Often this may be because He want you to be aware of that word you uttered from your lips. Mostly we utter this word out when we feel frustrated about the way things are going, when we are in dare need thing. But God ear is not far in those times too.
The truth is when God hear you this way, ensure you respond to Him with praise. When you notice this, it should give you confidence in the place of prayers that God always hear you. God does not honour one prayer than the other, God honours faith.