No. In fact, many sex crimes are committed without the victim being aware that they have taken place. Some examples include:
Indecent exposure of one’s genitals or other private parts in a public place
Voyeurism, which is watching or recording another without their knowledge, in a private area where they have a reasonable expectation of privacy, for purposes of sexual gratification or arousal
Taking or distributing pictures of another’s intimate parts, or of them engaged in intimate acts, without their consent