Rare card alert

 Today's rare card alert is a truly unique event for me.  In over eleven years of Postcrossing, I've never encountered such a situation.  I received a beautiful handmade card from a sender in the USA.  But when I tried to register the card, the Postcrossing web page returned an error message that I've never seen before:

The postcard US-11035043 is one you have sent!

If you have received a postcard with that Postcard ID written on it, it might be a thank you postcard from the recipient of your postcard.

You see, when there's a problem with a card ID number- when it's missing, illegible, or wrongly transcribed- the system tells you it's not a card that was assigned to be sent to you.  The correct card ID number can almost always be found by using the Postcrossing search page, where various bits of info like the country and town of origin, sending date, name of sender, etc. will allow a database search to return the correct number so the card can be registered.  But I've never had an ID number come back as one I've already sent, myself.  Turns out this ID number was a card I sent to a member in Germany in early January of this year.  Since this card was sent from the USA, it's not likely a "thank-you" card.  There was a written message with the card, from a sender named "Seren".  (This is the Postcrossing username of a member in Japan.  So, probably also not the card's sender.)  So as it stands, I have little to go on, and no way to register this card or thank Seren, the sender.  And that's a pity, as it was such a beautiful handmade card, a collage of intricately cut shapes in many layers.  And according to the written message, Seren and I have much in common: we are both Anthony Trollope fans, homebrewers, and work in biomedical research.  If you see this, Seren, thanks so very much for the impressive postcard!