"I mean it could be possible that a God doesn't exist and at the same time there's an objective morality we don't know about."
That is so arbitrary. There could be invisible pink unicorns. we just don't know about them.
If God doesn't exist, moral absolutes don't exist. Justify moral absolutes without God. You haven't done that. Morals would be based on individual opinions. There would be no universal standard for morality.
Without God how are you anything other than the coincidental, purposeless miscarriage of nature spinning round and round on a lonely planet in the
blackness of space for just a little while before you and all memory of your futile, pointless, meaningless life finally blinks out forever in the endless darkness?
The human value and morality of Atheism:
"There is no ultimate foundation for ethics, no ultimate meaning in life, and no free will for humans either.”
“No inherent moral or ethical laws exist… The universe cares nothing for us and we have no ultimate meaning in life.”
-“William Provine, -Atheist, Historian of Science.
“[T]here’s nothing, nothing, absolutely no reason for existing.”
-Jean Sartre, Atheist Existentialist, Philosopher.
“To live is to suffer, to survive is to find some meaning in the suffering.”
-Friedrich Nietzsche, Atheist, Nihilist, Philosopher.
“We are a meaningless collection of molecules, the only reason we exist is to promote our selfish genes, when we die, that's it” (and nothing ever mattered after-all)
-Richard Dawkins (atheist)
“In a universe of electrons and selfish genes, blind physical forces and genetic replication, some people are going to get hurt, other people are going to get lucky, and you won't find any rhyme or reason in it, nor any justice. The universe that we observe has precisely the properties we should expect if there is, at bottom, no design, no purpose, no evil, no good, nothing but pitiless indifference.”
-Richard Dawkins (atheist)
"Morality is no more … than an adaptation, and as such has the same status as such things as teeth and eyes and noses. ... [M]orality is a creation of the genes".
- Michael Ruse
Richard Dawkins: “We are survival machines—robot vehicles blindly programmed to preserve the selfish molecules known as genes.
The thing is, you know that moral absolutes do exist. The reason they do exist is because God exists. But you are trying to justify your Atheism. You are like a fish swimming about, denying the existence of water. You are trying to come up with a rational explanation for moral absolutes without God. Since you can't, your irrational explanation is "well, we just haven't discovered yet where moral absolutes come from".