I ordered from amazon upon open the package of the fly more combo. The drone itself is missing. The seller has the s/n. Can it be traced? I haven't registered it to me yet

I think you need to take this up with shipping and seller. Short answer no it can't be traced.

Wouldn't this be an Amazon issue?

Yup, got to go with dispute with Amazon/seller.
Amazon is pretty good about stuff like that,
the only other company like that, imho, is American Express, can't beat the support/buyer protection.......