How could something that's never been sold retail become 'no longer available'?
Just a guess: the Curl is in the pipeline, but NYCEwheels jumped the gun by listing it for delivery.
Know for sure: the Curl continues its 5+ year odyssey of not being ready for prime time.
I would take nycewheels stock status with a grain of salt. I ordered this item twice in the last year, in both cases it was not available despite the permanent "usually ships in the next business day' status.
http://www.nycewheels.com/brompton-a-seatp-alu.html
Their videos and Brompton selector are great though.