Where did Desiree come from?

From the text:

Why, it seemed but yesterday that Désirée was little more than a baby herself; when Monsieur in riding through the
gateway of Valmondé had found her lying asleep in the shadow of the big stone pillar.

Some people thought she might have strayed there of her own accord, for she was of the toddling age. The prevailing belief was that she had been purposely left by a party of Texans, whose canvas-covered wagon, late in the day, had
crossed the ferry that Coton Maïs kept, just below the plantation.