The phrase "accidentally met" is correct and usable in written English.
It can be used to describe an unplanned or unexpected encounter with someone.
Example: "I accidentally met my old friend at the coffee shop while I was waiting for my order."
Alternatives: "ran into" or "bumped into".
One day she accidentally met Peter Dobay & his wife as they got out of the train from Montreux.
"The twelve men congregated in the smoking room of the Crown Hotel gave the impression of a party accidentally met.
"I am a naturally peaceful person, but I wouldn't be that upset if 'Vladimir' accidentally met with a baseball bat," said one.
Several times, their eyes accidentally met, and then there poured into hers such a flood of feeling as she had never before experienced.
Although having had no contact for 20 years, on October 9, 2006 Pang accidentally met Ono in Iceland, on what would have been Lennon's 66th birthday.
In Los Angeles I had met his post-conviction girlfriend Lu, a German hippy girl with an obvious off-kilter sensibility who had come to America speaking little English and accidentally met some of the still-free "Manson girls" as the initial trial was taking place.
How she accidentally meets Warren Scofield, who's instantly smitten, I will not divulge.
"But my own feeling tells me that they didn't just accidentally meet up," he said.
Valeria, married to Fenton Hardcastle for six months, accidentally meets his first wife, Lois, in the bank.
Now, 20 years later, the two women accidentally meet again, reawakening their memories of a shared past.
They even set procedures for making sure that engineers and buyers from different clients do not accidentally meet one another while having lunch at company cafeterias here.
