It's not clear how Bernard planned to meet Ben and Jo if Hank hadn't accidentally grabbed the woman's headscarf. The Arab man who yells at them is implied to be under Bernard's employ, so what was his original purpose? Presumably the Arab man would have found some way to threaten or inconvenience the couple, allowing Bernard to intercede and gain their trust. Hank's accident just so happened to provide a perfect excuse.
He wasn't looking for Ben and Jo. He was looking for a "suspicious couple". This is more of a case of Fridge Logic, because if Hank hadn't accidentally grabbed the woman's scarf, Bernard would have never met Ben and Jo in the first place.