Is there any way the hair in my eyebrow can grow back after a direct unilateral browlift?

this is an interesting question and given it is so early, i'd advise you to give it some time. The odds are, the hair that was removed will not grow back, but you may be surprised once your brow "thickens" up a bit. I wish I had a better answer, but I think waiting is the key. 

With the direct browlift, the upper row of brow hair may either trimmed, or fall out with the procedure.  We try to bevel the incision so that the hair will then grow through the scar as it is healing.  So give it some time and hopefully the hair will return.    

Since you had your unilateral direct browlift only a week ago, I would say that your brow hair may grow back with more time.  I would wait at least 3-4 months to see if you get any improvement.  If there is no improvement, hair transplants are an option or you could try using Latisse on your brows to see if that helps.