Rebbe,
When my daughter was little she asked me that if goyim also have the indentation above their lips does that mean that the malach also taught them Torah pre natally?
Takeh - what is the answer to that?
B'kavod,
Sam Kosofsky
Firstly, I don't think it is clear from our Gemara that there is an indentation above a person's lips because he was hit by the Malach. It is possible the Malach hits him on his mouth in a symbolic fashion, but this does not cause the indentation on the lips. While I know it is a commonly stated "truth," I do not think it is a question on the Gemara but rather regarding what people say.
Secondly, even if it were true, it is possible that a Malach teaches Nochrim the seven Mitzvos that they must know, and that is a lot indeed. As I stated in Halachic World vol. 2 (Parshas Noach), according to the Ramban this includes many other Mitzvos as well such as withholding wages, overcharging, etc. There is a lot to learn. Therefore, if this is indeed true, it could be the reason.
All the best,
Yaakov Montrose