ElasticSearch self-referential structure, orphaned children - elasticsearch

Question

We have one index with one type, clients/client, and clients can be self-referential in a parent-child hierarchy (but not using ES parent-child, as that doesnt support a self-referential structure).
We are considering using nested for this, but the hierarchy is potentially endless, which makes nested queries a bit of a hassle, or maybe even impossible.
What we would want to find is primarily all top-level parents, so we build our searchQuery by filtering/searching for all elements that dont have a reference to parent (a simple term value with the parent id). Also, we save a reference to each elements children inside of that element, a list of children IDs, so that we can do subsequent requests in the frontend when the user sees that element, for a hierarchical visualization.
However, the thing that gives us a headache is: how do we, without post-processing, find children elements, where the parent WASN'T found, ie orphaned children, so that they dont get lost in the process? Because the above described query, finding top-level parents that each find their own children, doesnt work, if the search query matches ONLY a child element. The only idea we have is doing a second request for this, but that destroys the score sorting. We have been toying with many ideas, but have fallen short of finding a one-request-elasticsearch-solution for this issue. Is there such a thing?
our data looks something like below, but of course we can save the entire tree in each element. The question is, which is the best approach.
"hits": {
"total": 5,
"max_score": 1,
"hits": [
{
"_index": "clientsv3",
"_type": "client",
"_id": "5",
"_score": 1,
"_source": {
"name": "Client 2 sub2",
"country": "Belgium",
"parentId": 2
}
},
{
"_index": "clientsv3",
"_type": "client",
"_id": "2",
"_score": 1,
"_source": {
"name": "Client 2",
"country": "France",
"children": [
3,
5
]
}
},
{
"_index": "clientsv3",
"_type": "client",
"_id": "4",
"_score": 1,
"_source": {
"name": "Client 2 sub sub",
"country": "Germany",
"parentId": 3
}
},
{
"_index": "clientsv3",
"_type": "client",
"_id": "1",
"_score": 1,
"_source": {
"name": "Client 1",
"country": "Germany"
}
},
{
"_index": "clientsv3",
"_type": "client",
"_id": "3",
"_score": 1,
"_source": {
"name": "Client 2 sub",
"country": "Germany",
"children": [
4
],
"parentId": 2
}
}
]
}