Recruiter asked for references, I put three people forward, then two weeks of nothing

In every process I've been in, a reference request meant it was basically done. So I messaged three people, including a former manager I don't contact often, and asked them to expect a call.

Then silence. Followed up twice. Got a form rejection yesterday that didn't mention the references at all, so I have no idea whether anyone was ever contacted.

Now I get to go back to three people who did me a favour and tell them it went nowhere. Genuinely that's the part bothering me, not the rejection.

Do you warn your references every time they get requested, or only once you've got something in writing?