Ultrasound today. 2 sacks, 1 empty

I had an ultrasound today at 6 weeks. The tech should is that there is a baby growing, I'm thankful for that. But there were two sacks, one being empty. She said that it was most likely the start of twins, but one stopped developing. At first my logical mind understood and was thankful there was one little beating heart. After we left the appointment, I broke down. I am so sad to my core, that there was another baby that we won't be able to bring into this world. I didn't think I would feel this way, but I feel so heartbroken. My logical mind wants to tell me not to feel a loss because it was basically just cells, but my heart is so sad.