French phrase
Je suis tombé sur ~.
Meaning
I came across ___.
When to use it
Finding someone or something by chance. It works for people and things, with context identifying the referent.
Example dialogue
Je suis tombé sur un article intéressant en ligne.
I came across an interesting article online.
Tu peux me l'envoyer, s'il te plaît ?
Can you send it to me, please?