No, soap would prevent that from happening, and herpes requires direct skin to skin contact (mouth to genital, genital to genital, genital to anal) to transmit. It wouldn't transmit in the manner in which you describe.
Using soap is used to prevent transmission of lots of things, as you probably have heard over and over now.
https://www.nytimes.com/2018/06/22/well/can-a-bar-of-soap-transmit-infection.html
I don't know what was on your son's skin, but unless you or someone else is having sexual contact with him, it's not herpes.