As everyone else said, this should not be a finding. It could at best be a recommendation, and then you can consider if, as part of your risk-based program investigating these is the best use of your time to identify suspicious activity.
For the last few years, FinCEN and the regulators have been attempting to bring clarity to BSA requirements, and there are plenty of statements out there about the role of supervisory guidance and clarifications regarding when regulators will take action against banks. The updates to the FFIEC manual certainly support more clarity and less making up ticky-tacky errors just because they liked that another bank did it. Finally, the FinCEN request for comment on clarity for effective, risk-based programs, followed by the requirement in the NDAA that FinCEN does issue that clarity seems clear to me that this is not what the rule makers intend for their examiners to be doing.
Sorry, that's a bit of a rant and I didn't add to anything anyone said, but I've heard this too, and it's nonsense. FinCEN issues advisories for priority activity, and you should make sure your program reasonably conforms to those. As soon as FinCEN, or any authority in money laundering for that matter, says anything about unredeemed cashier's checks, then it'll be time to start adding processes. I bet there are hundreds of separate red flags tucked away in all of FinCEN's guidance, and I've never once seen this one.