I'm not a cue maker...... There is no excuse for ordering a cue and not paying in full upon completion. It's yours to do what you want with. Sell it and return the deposit less any expenses on your end. If they dealt again let them pay in full in advance. Who needs customers like that. It's your livelihood. Money is no joke.
I agree with Bishop's recommendation of saving the deposit for the next order.(If you choose to let them place another order) But why would you return the deposit?
Once a deposit has been sent, you are agreeing to purchase the goods as laid out in the contract. If you cannot filful your dutys as the customer, or cause damages to the seller via lost time/resources, than the deposit is forfeited, and right to the goods stay with the seller.
I say, give them a week to explain themselves, then post on AZB for us to buy!
And in future, make it clear from the getgo what you expect from the customer.