Will my hair grow back after BCC excision trauma?

I concur with Dr Surowitz.  There are no hair follicles in the scarred area so you will not regrow hair there.  The surrounding areas will likely regrow hair over time (recover from telogen efflvium).  You may have lost some follicles around the incision as well, depending on how it was sutured.  Grab some skin on your lower abdomen.  For most people, it is easy to get a handful.  Now try and grab some scalp.  It doesn't move much at all because there is a sturdy layer in the scalp called galea.  Galea doesn't stretch much at all.  When closing scalp defects, in order to get less tension (and avoid it falling apart), often flaps are created utilizing more incisions. A circular defect might be closed into something that looks like an 'S' or a 'Z'.  I just did one of these last week for a melanoma on my tennis partner!So, you could consider having the scar excised (recreate the defect - Ground 0)) and then having a flap closure.  Good luck.

Hair will not return in the area of your Mohs surgery, as it sounds that this healed by what is called second intention. The additional hair loss you describe sounds like telogen effluvium. This can occur after surgery, due to stress, and due to other issues including electrolyte and metabolic irregularities. If it is telogen effluvium, you have a very high probability of having normal re growth of the affected hair in 6-12 months. It is impossible to establish a diagnosis with examining the area. I recommend that you be seen by a dermatologist or a specialist in hair restoration for a evaluation and management of this.