For a search algo with reference return type, what should be the default return value?

Say I have an array, and I want to retrieve a reference to an element of this array.

struct A {
    int n;
}

A& search_algo(A* AList, int len, int target) {
    for (int i = 0; i < len; i++) {
        if (AList[i].n == target) { return AList[i]; }
    }
    return what?   //problem comes here, target not in array, what should I return
}

I would like to know what is the most conventional way to deal with it, or what return value makes the most sense. Like how can I best convey a message of "your thing isn't here, go away". Something similar to a nullptr would be great.

My current solution is to initialize a object A on the stack and return it. Although I can compile just fine, but returning a reference to local variable is unsafe.

I am thinking initializing the object on heap using new but that would be messy and I will have to deal with memory release. I don't like it.