Thank you for all of the comments!
Yes, several people have made comments on it, but they either think:
1. I lost weight
or
2. I dyed my hair. (uh, Joe, I had no hair... remember?)
It's obviously not a toupee, and people can't figure out that it is a transplant. I think they just don't have a mental schema for hair growing back once it's gone, so their mind picks up something familiar to account for the difference (like the above).
For some reason no one has guessed Propecia yet...