Need help with wording thank you card.?

Why do you need to tell her you returned it? She gave it, you loved it. That's all that needs to be mentioned in a thank you note. She already knows about the other bassinet and can probably assume its sentimental value. Don't break her heart any more by telling her that the one she got you is no longer in your possession. Also, you are correct in saying that there is no polite way to thank someone for getting you the most expensive gift off of your registry.