In one of the sweeter family gestures ever devised, for the past 33 years, a father and daughter—who live about 65 miles apart outside of London—have been mailing the same birthday card back and forth for 33 years, adding something new before each post. But now it’s been lost in the mail.

According to the BBC, the card was first sent by Claire Fuller to her father Stephen in 1984. The card features an image of a sad duckling in a yellow rain jacket and red wellingtons, looking forlornly into a puddle, with a simple “Happy Birthday” printed on the inside.

The next year, on her 18th birthday, her father added a new message and gave the card back, and they’ve been going back and forth between each other in that way every year since. Each time they send it, they add another message, in smaller and smaller type, as room on the card continues to dwindle, and the cardstock gets more frail.

But this year, Stephen sent it off on February 10th, and it has yet to materialize at Claire’s place. After thousands on social media called for the Royal Mail to look into the card’s whereabouts, they said that they are trying to track it. Hopefully, that little duck won’t be lost for long.