Hello XXXXXXX,
Yes, I believe you are obligated to redeliver the 1st product. You entered into two separate and distinct contracts of sale since they were on different dates and not part of the same transaction. Just because someone breaches a contract on one of the contracts does relieve you of your responsibility to perform on the other contract (the first sale). As long as it was understood as part of the first sale that you were required to redeliver because of lost links then you are required to do so to meet your obligations under the first contract of sale. Your remedy to recover on the second sale is a breach of contract action on that sale.
Thomas
Lawyer
Seventeen years experience as New York, New Jersey lawyer, and publisher of online legal newspaper