A person who is a Musafir whilst still travelling [in a car] but out of his town prays his Isha sitting i.e. in the car, is his prayer sound? i ask this because he had the option of praying standing when he returns home [the same night within the Isha time]? also bare in mind there weren't any places for him to pray at the destination i.e. if he did pray he would have had to pray on the streets.