Novichok is a BATTLE POISONING GAS it cannot harm one person inside a plane or his cup of tea or as in Skripal’s case, rub the door handle with it. It is a gas and weapon of mass destruction it cannot harm specifically one person.
The poisoning doesn’t make any sense because Russia special services have a tradition of killing their enemies and terrorist like they did with Trotsky, Konovalets, Bandera. If Skripal had been a missed target for them, they wouldn’t have use the same technique for Navalny. There are many simple and efficient techniques to kill someone and bury his body in the forest. But Navalny was deep in debts (t 30 million roubles according to court decisions) and interested nobody.