Parshas Miketz I: What Did Binyamin Know?

The pashtus is that Binyamin did not know what happened to Yosef. After all, he wasn’t there when Yosef was sold and moreover, the brothers had taken a shevuah that they wouldn’t tell anyone. Yet we find that the gemara in Sotah 36B (and quoted by Rashi in Parshas Miketz) says that Binyamin named his 10 sons in "honor" of Yosef. Two of his sons were named for the fact that Yosef was sold in captivity and living in a strange land. This would imply that Binyamin did know that Yosef was sold. How did Binyamin know? I checked the Artscroll (es chatai ani mazkir hayom) and in the footnotes it brings down from the Maskil L’Dovid and Tanchuma Yashan that Binyamin knew thru ruach hakodesh that Yosef was sold.