What do I do about this dilemma? (See details)

My husband and I were invited to a wedding in August, but at the last minute could not go due to a family emergency.

We had registered on the couple’s gift registry to get them a teapot that they wanted. But I had not yet sent the teapot (relying on the etiquette rule that you have up to one year to send wedding gifts).

Yesterday in the mail we got a thank you postcard with a picture of the couple on the front thanking us for the teapot and saying they were sorry that we had to miss the wedding and they hoped to see us soon.

Do I:

1. Just send the teapot now with no comment?

2. Tell them that we had not yet sent the teapot and they must be thanking us for a teapot from someone else?

3. Something else?