In most US states, the scenario creates a binding contract and you would owe me money (not sure about Louisiana though). My note and shipment is an offer, and your retention/sale is an acceptance. See info between the lines
(1) A contract for sale of goods may be made in any manner sufficient to show agreement, including offer and acceptance, conduct by both parties which recognizes the existence of a contract [...]
(2) An agreement sufficient to constitute a contract for sale may be found even if the moment of its making is undetermined.
(1) Acceptance of goods occurs when the buyer [...]
(b) fails to make an effective rejection [of goods], but such acceptance does not occur until the buyer has had a reasonable opportunity to inspect them; or
(c) does any act inconsistent with seller's ownership;
Contracts do not have to be in writing. They can be inferred by conduct and they can be oral. A court can also create an implied contract in situations if required by fairness (i.e. to remedy fraud or some other bad conduct causing unjust enrichment or loss).
Also, just because a contract exists doesn't mean that the contract is a complete integration of the parties' intentions or all terms. We can make an oral contract and then sign a piece of paper saying that a contract exists. You only need a writing in modern society in certain situations, and even then it's possible to get around that requirement in some cases.
If you believe in the NAP then you must believe that implied contracts are allowed. Otherwise you are allowing people to essentially get away with theft just because there isn't a signed piece of paper. Signed paper doesn't negate harm or culpability.