[MaulingMonkey]

> If everyone is aware of what went wrong

Big assumption. Chances are at least someone was out on vacation or something. A postmortem can help spread the word - and perhaps calm those downstream who weren't in the loop as much, through a show of clear and open communication and ownership, instead of trying to bury it.

> and the issue is unlikely to ever happen again,

Also a big assumption. You can almost certainly https://en.wikipedia.org/wiki/Five_whys your way into a broader pattern of something that will happen again, and can review what worked to expectations, what didn't, what should be improved, and what can be left alone - even if it perhaps will happen again - perhaps being more expensive to try and fix, than to merely accept the occasional failure as an acceptable price of doing business.