There is both a visual and aural indicator. That being said, nobody (except Bonin) knew that the PF had his stick completely back until it was too late.
That stuff is really interesting, I've been digging through random reports, documents and manuals for two hours now.
Yeah, it really is. If you haven't already, check out the full BEA report - it's incredibly comprehensive and leads to lots of "jumping off" points for further research.