1
general::
Also, chance upon. Happen upon, find or meet accidentally, as in In Paris we chanced on a wonderful little restaurant, or Andrew chanced upon his karate teacher in the health-food store. [Mid-1500s]
American Heritage Idioms
2
general::
Phrase(s): chance (up)on someone or something
to find someone or something by accident; to happen on someone or something. (Upon is formal and less commonly used than on.) • I chanced upon a nice little restaurant on my walk today. • I chanced on an old friend of yours in town today.
McGrawhill's American Idioms And Phrasal Verbs