Is something only a lie if you believe it to be a lie?

let's say you ask me if i can give you a dollar. i have a dollar in my coat pocket but don't realize it. not realizing i have a dollar in my pocket, i tell you i don't have a dollar to spare. would you say i lied? i would think most people would say no to this scenario. so how is it anyone can claim i'm breaking any of the commandments pertaining to worshipping god, if i do not believe such a being exists? and if i don't believe a god exists, then i certainly can't say that such a being gave me any of the other commandments to follow. therefore that absolves me of any other sin as well, since sin is defined as disobedience of god. i can't very well be disobeying him, if i don't believe he exists. so there you have it, i'm sin free. whenever any god wants to test my obedience, he can email me. to those who consider this testing god, do you really think so low of him to consider sending an email a test for something that's presumably omnipotent?