I’m worried about the density

I had a hair transplant 21 days ago, and as I looked closely, I saw many gaps where there are no grafts.  Did my surgeon not give me what I bought?

By the 21st day, I expect that many grafts will fall out in the ordinary course of healing. You didn’t mention how many grafts were put in, but these spaces probably had grafts in them. As they are shed after a hair transplant between 2 and 5 weeks after the procedure, they will grow when they go into their growth phase, usually 2-4 months from the day of surgery. You will know the fullness at 5-7 months from the surgery date.  Don’t worry about this, as it should be okay if your surgeon’s team did it well.