A complete search of the internet has found these results:
what happened to is the most popular phrase on the web.
In these phrases, "to" and "with" have different meanings depending on the circumstance in which this phrase is used. "What happened to" is usually used in reference to a specific person, group of people, or specific place. "What happened with" is usually used to refer to a situation or event.
77,900,000 results on the web
Not after what happened to Wesley.
You saw what happened to Terry.
So, what happened to James Woods?
Because that's what happened to LawrenceJones.
I meant what happened to the person.
Not after what happened to Victor.
Claire, what happened to your dad after the party last night?
I heard about what happened to Hanson. I'm so sorry.
Shame what happened to your cousin.
I want to ask you about what happened to your wife.
I regret now what happened to More.
Nobody knows what happened to her.
What happened to this theme park? It used to be so nice.
10,400,000 results on the web
We heard what happened with the hostage situation.
Sorry for what happened with the festival last night.
Look what happened with Ultron and Wonderman.
I forgot to tell you what happened with Rachel at school today.
Tell me what happened with Landon Wale.
Mr. Munroe, tell us, whatever happened with this city's parks?
That's what happened with the Kennedy assassination.
This is exactly what happened with Kirsty.
You saw what happened with the second Capote.
And you figure out what happened with utz.
This is exactly what happened with the Iraq war.
The other part is what happened with the elevator.
I gotta tell you about what happened with Porter and his experiment--there was an accident.
GRETCHEN: Look, what happened with Billy was not important, I promise!
I heard what happened with the Crowders' old place.
I heard about what happened with your uncle's bar. That's a shame.