Incidents of this type are exactly why military men despise war correspondents. You capture valuable intelligence assets, and some jackass newspaperman who wants a story goes and tells the whole world about it. Note the date, this story was being told to the whole world just a month after the Queen was captured, and the Yankees no doubt changed their signals shortly thereafter. Any value this item had to the Confederacy was quickly lost. (And knowing Charles Rivers Ellet, commander of the Queen, he probably didn't mention the fact that he'd left the signal book in the boat to any of his superiors.)