Blown off course
To be blown off course in the sailing ship era meant be to diverted by unexpected winds, getting lost possibly to shipwreck or to a new destination. In the ancient world, this was especially a great danger before the maturation of the Maritime Silk Road in the Early Middle Ages, finding expression in the writing of Cosmas Indicopleustes. Even in later eras, the ship could attempt to limit its divergence by tacking or heaving to, but it was often difficult to keep track by mere celestial navigation before the invention of the marine chronometer in the late 18th century.
A number of "discoveries" during the Age of Discovery were accidentally found in this way, and the serendipity of being blown off course is also a common trope in fiction. Accidental discovery may have played a larger role than previously acknowledged in early European colonialism in contrast to the idea of a centrally-planned program as by Prince Henry the Navigator, but it is also thought that the Austronesian expansion was more directed and purposeful than once thought.