Hair removed from hairline by accident - when will I know if it will grow back?

Hello and thank you for your photos.  Did you laser your upper back and the back of your neck too?  Because there is no way the laser treatment from upper back/shoulder area would affect hair in the back of your neck.  The LHR process is semipermanent  and hair will grow back but it will be a long time. Now, you should look into PRP for hair regrowth as you seem like a perfect candidate for thinning hair in the back of your neck.  Hope this helps. Best. Dr.Avaliani

Hair on various parts of the body grows at different growth rates.  You would have to be treated more than one time in that area to have permanent hair loss.  I would consider PRP with microneedling to add growth factors to this area coupled with topical Minoxidil therapy to help grow back your hair.  Please consult an expert in hair restoration.  Best, Dr. Green

A single hair removal treatment usually only impacts 5-20% of the hair in the area treated, so even if there was an error in aiming, the entire area should not be affected.