In The Star Beast by Robert Heinlein, published in the early '50s, John Thomas Stuart is a high-school student who keeps an exotic animal named Lummox that his great-great-grandfather brought to Earth from a far-away planet. Lummox one day escapes from his paddock and eats the neighbor's car and damages buildings, so lawsuits get filed. When a court of law is being asked to order the animal destroyed because it's dangerous, beings from a distant planet are contacting Earth's government to say a child belonging to their royal family is missing and is thought to be on Earth.
The story was translated into German by Waltraud Götting.
In English many verbs can be used either transitively or intransitively: "I boiled the water." or "The water boiled.", so that the verb "boil" refers either to what I did to the water or to what the water did. Likewise "The farmer grew broccoli." or "Broccoli grew in those fields."
Little did John Thomas Stuart suspect that creatures of Lummox's species reaching a certain age grew arms. So when that happened, he was surprised. The reader sees this:
Lummox had grown an arm.
This is a transitive verb. But if I say "The boy grew three inches.", then it's intransitive; "three inches" is not the object of the verb, it's not the thing that the "growing" was done to.
Götting's translation says:
Lummox war ein Arm gewachsen.
With transitive verbs, one more often sees "hatte" rather than "war", and the common noun phrase "ein Arm" is in the nominative case, so it can't be the object of the verb. What then, is its syntactic role in this sentence? Is it like the "three inches" mentioned above? And where, in accounts of German grammar, does one find tha the nominative case is used for such an occasion? What would be other examples of the nominative case being used for a noun phrase playing that sort of role in a sentence?