(Xanathar's Guide to Everything, page 28)
Under Arcane Shot, during the first description of the functionality, it indicates:
Once per turn when you shoot an arrow from a short bow or a long bow as part of the Attack action, you can apply any of your Arcane Shot options to that arrow. You decide to use the option when the arrow hits a creature, unless the option does not involve an attack roll. You have two uses of this ability, and you recover all the uses spent when you finish a short or a long rest.
And it says:
You imbue your arrow with force energy drawn from the school of evocation. Energy explodes after your attack. Immediately after the arrow hit the creature, the target and all other creatures within 10 feet of it take 2d6 points of force damage each.
So I don't think you are using the functionality until you know that the attack was successful, so you would not lose the functionality if you missed it.