Hi Laura in London,
I'm sorry you are going through this. It must be very difficult. I will do my best to help.
Not having any photos to look at, I can think of two possibilities. Some surgeons will shave the hair around the sideburn area to make it easier to sew the incision back together, as well as assisting in suture removal at the one week mark. If the surgeon performed a short scar facelift, there should be an incision horizontally under or within the sideburn hair. If you can see an horizontal or curved incision extending from the top of ear towards the corner of the eyes, as well as some shaved hair above and below the incision. If this is the case, then it will take some time for the shaved area to grow back fully.
Another possibility with this type of incision is that there is a lot of tension on the incision below the sideburn, and as the skin stretches, the widening scar does not grow hair, and will appear to be a bald spot within the hair above it and the hair below it.
The other possibility is that the incision is vertical deep inside the hairline directly above the top of the ear. The incision is intentionally hidden inside the hairline. Depending on the patient, sometimes there is so much looseness of the cheeks, that as the cheek skin slides back, a significant amount of the side burn hair gets pushed back toward the vertical incision and when the surgeon trims the excess skin, the patient appears to have lost their sideburns.
I don't know which is the case for you.
Best,
Dr. Yang