In August, Mrs Searle posted two items she had made for Prince George - a knitted red cardigan and a traditional-styled cotton sailor suit - to the couple's residence, St James's Palace in London.
The card she received had a photograph of Prince William, his wife Catherine and Prince George on the front, and a printed message on the back which said the duke and duchess were ''most touched by the thoughtful gift''.
''Their Royal Highnesses are overwhelmed by all the wonderful messages and gifts they have received and send you their warmest thanks and best wishes,'' it read.
Mrs Searle said she was ''very thrilled'' by the card and would have it, the envelope it came in, and photographs of her handcrafts framed as a memento.
She said she would now be watching media coverage of the couple and Prince George closely to see if he was wearing her garments.
The duke and duchess have been inundated with gifts from around the world. New Zealand's official gift was a hand-spun and hand-knitted merino shawl.
