What is the ruling regarding making up prayers for someone who had a wet dream during the day in Ramadan and did not realize it until just before the Maghrib call to prayer?

Whoever finds semen on his clothes after sleep must perform ghusl and repeat the prayers from the last sleep he had. This is based on the hadith of Aisha (may Allah be pleased with her) that the Prophet (peace be upon him) said concerning one who finds wetness but does not remember a wet dream: "He must perform ghusl." The fast is valid and is not harmed by a wet dream.