What is the ruling on the fast of one who claims to have had a wet dream as a result of an unintentional touch from a girl in crowded transportation, and found a viscous fluid on his clothes?

Al-madhy is a sticky fluid that is discharged when one has sexual thoughts but not with gushing desire. What was discharged from your friend is madhy due to touching, and his fast is valid according to the most preponderant opinion. Al-madhy is impure, nullifies ablution, and necessitates washing the male organ only, according to the most preponderant opinion.