I’ve had significant shock loss after a forehead lowering procedure. What is the likelihood it will grow back? (Photo)

If you are having issues after your surgery, the best person to ask is your surgeon who knows the specifics of your surgery.
Shock loss is always a risk and it is difficult to assess this on the Internet or with photos.  You need a before and after comparison. You need an examination.

Dear JZ, I am sorry that you are having this shockloss. The 3 week timeline is relatively typical of this type of loss. The good news is that shockloss is usually temporary, but as you know, hair takes time to grow back slowly. You may wish to see a hair surgeon to evaluate you. There may be several treatment options to help speed the recovery a bit.  I wish you success with your recovery!

If you are a female, it is likely that the hair will come back but if you are a male, it is unlikely as this can precipitated genetic hair loss from the shock.  For women, all of the hair along the scar may not return which means that you would require a hair transplant to hide the scar.