Shock loss hair on top of head after Bosley treatment. How long will it take to get thick hair back? (Photo)

It takes several weeks to months before the hair usually grows back.  Shock loss is due to the loss of normal hair whether it is from donor site or recipient area.  It can occur with both FUE and strip procedures.  Usually if it occurs it will take place in the recipient area.  
Shock loss from hair transplant can occur due to the following:
Anesthesia-  excessively long procedures taking longer than 12 hours can induce shock loss more likely.  the repeated use of lidocaine, marcaine, and perhaps most importantly epinephrine can affect nourishment of the hairTraumatic harvest-  In strip surgery, traumatic harvest can induce shock loss.  Recipient area trauma- during the incision making process the hairs are either crushed or cut and damaged during the process.Ways to minimize shock loss are as follows:
Improve recipient bed and donor area environment.  Make your recipient environment improved by addition of growth factors and/or PRP to help reduce incidence of shock loss to native hairs.Use of Rogaine and Propecia- can help miniaturized hair become more stable and less likely to fall out during procedure9xRobotArtas-  The latest version of the robot can make recipient sites and can determine angle of existing hair and help ensure that the angle will not damage existing hair.  Especially helpful in patients where you are transplanting hair to create densityMinimize anesthesia time and procedure time- We limit number of grafts to a safe number per session.  Extended anesthesia periods and harvest times can cause patients to have a higher chance of shock loss.  The 9x Robot harvests between 1000-1500 grafts per hour making it superior to previous additions and traditional FUE approaches.Best,
Anil Shah

Shock hair loss after surgery can happen.  There isn't much your husband can do at this point.  If the surgery was planned well he should see positive results in 6 to 12 months.

Shock loss is not uncommon. In most patients the follicles will recover. However, it can take 3-6 months for the follicles to grow a new hair shaft.

Unfortunately shock loss can be very common in both FUE and FUT hair transplant procedures if slit incisions are made to transplant the hairs.  In my opinion this is an outdated approach, but many clinics still use this method.  The procedure is thus:  after applying anesthesia to the donor area, micro incisions are made in the scalp using a specialized blade and then the grafts are put into these pre-made sites.  The problem is that making the slit sites disturb existing hair follicles and they become traumatized and shed their hair - leading to what is know as "shock loss."To prevent this, I recommend the use of specialized implanters which avoid the need for making slit incisions.  I also recommend the use of growth factors with every surgery.  I never have shock loss with my technique.  The website below has some information on my technique. The good news is that most of the time, hair shed from shock loss will grow back.  It will just take time and patience. Best, Dr. Welter

What your husband is experiencing is very common and can be very distressing. (I know this first hand.) The more hair you have in the area of thinning prior to the transplant (the less bald you are), the more likely it is for shock loss to occur and the more likely it is to be noticeable. There is very little your husband could have done to make things worse (other than pulling his hair out). If he is not already on Propecia (finasteride) and/or minoxidil, and/or using a laser device, this is something he could discuss with his surgeon. He could also try one of a number of camouflaging products that are available (e.g., Toppik). Though much of the shock loss is likely to recover over the next 3-4 months, and this will be supplemented by growth of the transplanted hair, it is unrealistic to think that his hair will be as thick as it was in his twenties.

Shedding
after a hair transplant is almost always prevented by the drug propecia. If the shedding is in the transplanted area, the new grafts, when they
grow, will off set it. If the shedding is from other areas in the front and top of
the head, shock loss usually accelerates the hair loss that
you might have seen two years after a hair transplant. The hair loss that occurs from acceleration in miniaturized hairs, often do not return in young men. At 30, you just have to wait it out until the new hair grows in and if the shock loss reverses, it will happen at the same time.