Your "Happiness Always" card is in the Mother's Day gallery now, about the tenth one down when I checked. Maybe there was a delay before the gallery updated to include it.
Another possibility is that your browser might be showing you an older, cached copy of that gallery's index page. If you're still not seeing your card's thumbnail, you can do a hard reload of the page. Instructions for various browsers are on Wikipedia,
http://en.wikipedia.org/wiki/Bypass_your_cache . You only need to "Reload a page and bypass the cache," not completely clear your entire cache.