I am not 100 percent sure what you are saying here.The flaw in this argument is that you are claiming determinism based on your knowledge of the coin flip result. However, if you flip a coin and cover it with your hand, isn’t the result also deterministic? You don’t know the result, but the coin does! Substituting the coins knowledge for your knowledge doesn’t make the event deterministic.
Are you saying that any event that takes place, after it takes place, is deterministic, or in the case of the coin are you saying a coin flip is deterministic or none deterministic?
Let's attach a thin shaft to one edge of the coin so it sticks out the side in the same plane as the disk.
Then let's stick the shaft in a portable drill with a battery pack and turn it on so that the coin continuously flips from heads to tails, and back again, etc., etc.
Do you see anything deterministic about the coin in that case?
What about if the battery runs out and the drill chuck stops at a random angle?