Accessing Threads by core_v2_forumThread.List

I am having some issues getting expected data from core_v2_forumThread.List({});

Here is my code:

var forumThread = core_v2_forumThread.Get(557384);

if(forumThread == null || forumThread.HasErrors())
	return;
	
var threadCount = core_v2_forumThread.List({ AuthorId: forumThread.Author.Id }).TotalCount;
return threadCount;

I have verified that forumThread.Author.Id returns the correct data. I have spot checked with a few different Thread Id's and I cannot get core_v2_forumThread.List to return any data. Its not throwing any errors or warnings if i return the List

PageSize: 20 [number]
PageIndex: 0 [number]
TotalCount: 0 [number]
Warnings [array]
[]
Errors [array]
[]
Count: 0 [number]
IsReadOnly: false [boolean]

The API documentation mentions that there is a List Overload 4 which accepts the AuthorId.