This is the 9303rd most frequent Russian word.
стивеном
"Стивеном" is the instrumental case of the Russian male name "Стивен" (Steven).
The word 'стивеном' here is used as an instrumental case to indicate with whom the meeting occurred.
Я встретился со Стивеном вчера вечером.
I met Steven yesterday evening.
In this sentence, 'стивеном' is also in the instrumental case, showing accompaniment in the action.
Мы обсуждали планы со Стивеном в кафе.
We discussed plans with Steven at the café.
Here, 'стивеном' indicates agency, showing who organized the trip (also instrumental case).