Samoa's points came from flyhalf Patrick Fa'apale's penalty and center Rey Lee-Lo's try that caught France napping at the start of the second half.
Vakatawa broke into the France team in the Six Nations despite being a contracted sevens player. He does not play for a club in France's elite Top 14, and had not even played since representing France at the Rio de Janeiro Olympics in August.
But he showed little signs of rustiness with well-taken tries, two of them in the second half.
Trinh-Duc came off following a tackle from winger Paul Perez, who was playing at the ground where he plays his rugby for Toulouse, and was among Samoa's best players.
Playing tough-tackling Samoa is one of the most physical challenges in rugby, and France certainly felt it.
Prop Jefferson Poirot hurt his shoulder and center Remi Lamerat also came off with a knock at the same time as Trinh-Duc.
- AAP