I incidentally saw dry traces of semen on my underwear. This means that I must have had a wet dream, but I did not feel it. I cannot remember when this happened. What is the ruling on my prayer, fasting, and recitation of the Quran if my wet dream happened some time ago, maybe two days back, since the last time I made ghusl (ritual shower for purification)?

All perfect praise be to Allah, the Lord of the worlds. I testify that there is none worthy of worship except Allah and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and Messenger.

It is obligatory for you to repeat all the prayers of which you are certain that you prayed them after your wet dream. In addition, it is recommended that you repeat all the prayers that were possibly offered after the wet dream. In his An-Nihaayah, Ar-Ramli said:

If a person sees traces of semen on his clothes or on a bed that he does not share with anybody else, then he is required to perform ghusl even though he does not remember whether or not he had a wet dream. The person is required to repeat each obligatory prayer of which he is sure that he offered it after having experienced the wet dream. The person is, however, recommended (not required) to repeat each prayer that was probably (not surely) offered after having experienced the wet dream.

In this situation, it is certain that the wet dream must have taken place the last time that the person was sleeping. This is so given that the act whose time is not definitely known should be referred to the closest possible time.

As far as fasting and the recitation of the Quran are concerned, there should be no problem given that experiencing wet dreams does not nullify one's fast. Moreover, one is not sinful for reciting the Quran while ritually impure out of forgetfulness.

Allaah Knows best.