In John 8 vs 3, a woman was made to stand before Jesus after being caught in an act of adultery but there is no mention of the man. Why is that?
The reason for‘ no man’ is in the reason for this account. It wasn’t about the adultery .... at all. It was about the Law.
The Pharisees were trying to have Jesus violate (speak against) the Law. Jesus had to fulfil the Law, both as a Rabbi, and as a ‘man’ having to fully ‘keep’ the Law.
Jesus was going about preaching grace and Mercy, but could not be allowed to use this against the Law. The penalty for adultery was death by stoning, and Jesus had to agree - and he did! He could not say No!
Jesus could not Let her ‘off’, nor exercise Mercy - the Law has no room for Grace nor Mercy. He had to demand what the Law demanded - it was his Fathers Law! If, through compassion, he went against the Law, he would have been a ‘bleamished’ sacrifice.
The Pharisees thought they had set up the perfect snare to have Jesus break the Law, thereby ‘legally’ having an excuse to put him to death - (a Rabbi not enforcing the Law was breaking it.) - which was their intent.
In John 8:1-11, not mentioning the man involved in this clear Jewish setup, was part of the plot. The woman was used and the man was very possibly one of the accusers who wanted to "frame" Jesus by trapping Him (v6).
In fact, their actions, in themselves were also illegal under Torah. If anyone saw that a crime was to be committed (v4), that person should make every effort to avoid the crime being committed. Therefore the accusers were as guilty as the woman they were accusing, especially the man involved!
It was such provisions that made it almost impossible to accuse someone of a crime worthy of the death penalty because several witness must observe the crime and such must try to prevent the crime being committed.
Jesus was also correct that the one who had no sin was to be the first to cast stones; none did because all knew they were themselves guilty.
None of this says that the woman was innocent; only used to trap Jesus. Jesus approached the situation in such a way as to save both the woman and the accusers. All left chagrined (v9), but the woman left to presumably begin a new life (V11).