The Only Matilda in the World
There’s nothing too awkward about this story. The OP heard their childhood name being called from a distance and thought that it was a family member who came to Disney World to surprise them. Sorry to burst your bubble, OP, but your family doesn’t love you enough to fly down to Florida and pay you a visit.
Also, is Matilda really that uncommon a name? It probably is; we only know of one Matilda, and she’s a storybook character. Unless you were craning your neck like a gazelle around a pond looking for nearby predators, you have nothing to be embarrassed about.