uuhhhmmmm surprise. You couldn't find a method for this because there is none. You have to implement a hql for this yourself
We had to implement several of these functions, and finally had to go back down to the level of sql direct to get these kind of advanced queries, but it is really necessary for a nice display list for the inbox.
Another reason is the paging and sorting was not going well, so had to be pushed down to the sql level.