Sexual energy is not merely physical. There is the energy of the sacred sperm, and the brute matter. Women can lose seminal fluids, physically and energetically, through orgasm.
Seminal emissions for both men and women, therefore, engender succubi and incubi. Because the sexual energy creates, the quality of our mind determines how that energy is polarized, whether for diabolic or heavenly creations.
Black magicians have procedures by which to reabsorb spilled semen. Samael Aun Weor never explained these techniques so as to not give weapons to the foolish.
As for what occurs to semen when spilled, read the article below:
For thirty years I sought God. But when I looked carefully I found that in reality God was the seeker and I the sought. -Bayazid al-Bastami