It takes a really strong atheist not to call out to God in their moment of need. A number of people have told me how when they/their children were ill they have called out to God "If you're real, if you are there, please help me?" but then once things are fine we can forget to say thank you and keep saying thank you. There is a lovely part of the service at our church - where it says "Say thank you to God" and it's a good reminder to do that each week.
Today I said that prayer "God, please help" and thought how often have I sinned (my arrow has fallen short or I have strayed from the path - to give an accurate definition of sin) and not said "sorry" to God. We so often want his help on our terms and then slip back into our secular world.