Is ghusl obligatory if a person wakes up from sleep and finds wetness and moisture in his clothes, believing it to be semen, but without the stickiness or distinctive smell of semen?

Scholars have agreed that whoever experiences a wet dream but does not see any semen is not required to perform ghusl (ritual bath), because the obligation of ghusl in a wet dream is contingent on the emission of semen, based on the Prophet's (peace be upon him) saying: "Water is from water." What you have mentioned is nothing more than a delusion, and it is inconceivable for semen to be found on outer garments without being on inner ones. Therefore, we advise you to disregard these delusions. If, hypothetically, the emission of semen were to be assumed, the default state is the preservation of ritual purity, which is a certainty that is not dispelled by doubt. The proof for this is the hadith: "He should not leave until he hears a sound or finds a smell." Accordingly, ghusl is not obligatory for you due to your lack of certainty regarding the emission of semen.