Doubts on having a wet dream
In the name of Allah, the most Beneficent, the most Merciful.
Answer
Saaidah Aaisha Radiallahu Anha relates that the Prophet of Allah Sallallahu Alahi Wasalam was asked about a man who finds wetness (semen from ejaculation) but does not remember having a wet dream. So He Sallallahu Alahi Wasalam said, “he must perform ghusul” and he was asked about a man who thinks he had a wet dream but finds not wetness. So He Sallallahu Alayhi Wasalam said: “he does not have to perform ghusul.” So Umm Sulaim Radiallahu Anha asked, if a woman finds wetness, does she have to perform ghusul? He said: “yes, women are the partners of men.” (Sunan Abi Dawud p.35 v.1)
With regards to your question, if you’re under garment is dry then ghusul will not be compulsory upon you even though you may think to have had a wet dream.
Only Allah Knows Best
Mohammed Tosir Miah
Darul Ifta Birmingham