From June 24th, as Bill and Arthur discuss Dean Thomas and how to bring his real half-blood ancestry to light and get him out of the camps.

Arthur: The only problem, of course, is how do I find the Auror case number?
Bill: I've been trying, but I still don't have a trustworthy conduit of information into that department.

(Even if they'd made contact with Rachel at that point, she should've been in training in Y1, not actually an Auror yet.)