All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His Slave and Messenger.
First of all, we say that your previous questions together with this question indicate that you are suffering from severe Waswaas (obsessive whispers), and we cannot do anything but supplicate Allaah to heal you from this affliction of severe whispers regarding impurity.
We know from experience that getting carried away with someone who has whispers and answering all his question is of no end, and it only increases his whispers, especially if the problem that he has contradicts what has been agreed upon by rational people.
The best example regarding what we are saying is this very question, as you are presuming the probability of the existence of invisible blood with the mucus. These are the very whispers! We know about the existence of blood only when the blood can be seen, and a small amount of blood is excusable according to the view of many scholars, while they have differed about the exact small amount that is excusable.
Therefore, dear questioner, please stop this and fear Allaah and do not overburden yourself and overburden us with such questions as we have many important questions whose askers are waiting for an answer.
However, if you mean that the mucus touched an impure place and it became impure by it, then if you touch the impure mucus with your hand, then in this case, it can be ruled that your hand became impure, and it is enough for you to wash your hand. Not everything that you touch with your hand before washing it becomes impure unless you are sure that the mucus in your hand came into direct contact with it.
Allaah Knows best.