> “Since the initial work of Balabanova et. al., other studies have revealed the same drugs (cocaine, nicotine, and hashish) in Egyptian mummies, confirming the original results."
They were a bureaucratic society. To cross the central rainforest and the Kalahari desert to trade with South Africa and do not reflect it in their documents seems unlikely to me (but I'm not an expert in this field).
This said, finding a wild Nicotiana in Egypt today is a childs game. Nicotiana glauca, an escaped american species appears everywhere in all Mediterranean countries. Could easily slip into any local plant mix aiming to give some good ol' autenthicity to a modern mummy.
The first ships likely capable of making a crossing are the Chinese junks, followed by Polynesian outrigger canoes. The first European ships capable of making it are probably the Viking longships, which makes pre-Viking contact difficult to conceive, much less a sustained trading pattern. Furthermore, Phoenician ships were predominantly rowed, not sailed, which makes the journey especially hard to believe.
In theory is possible. There is one species of Nicotiana native from Africa (Nicotiana africana). The problem is that this plant is a Namibian endemism, in the other coin of Africa. For people mastering the complicated process of embalm a body, with a trading area that extends to the entire Mediterranean sea, and taking a lot of precise steps and hassles to be sucessful, a local plant able to stop insect damage would had been noticed and treasured. We can speculate that the current Namibian populations are relict populations of a much wider distribution area, and that this is another white rhino. Maybe the north populations were wiped by the old Egyptian empire?, then the flower must appear painted somewhere or some obscure text should talk about such treasure.
And in any case, there is still the Cocaine issue. There are also some members of the family Erytroxylaceae native from Africa, but If you find three of the most popular drugs when putting a sample of a mummy in a machine, you should suspect that either the mummies were fake, or where real but used later to smuggle drugs, or that the drugs were into the machine previously (the laboratory has been used before for analyze drugs).