Corrected entry: During the chase after the stock exchange attack, Batman ends up flying the batwing out from an alleyway after being chased there by police. But it can't fly itself (part of the plot) and the attack took place during the day, meaning that even if Batman somehow planned for this, he must have just stuck the batwing in an alley for a fairly long period of time and somehow no-one stumbled across it, despite being in a busy part of the city.
Trivia: In the scene where John Blake visits Bruce Wayne in his mansion, you can see a bust of C-3PO behind Blake and to his right. As Blake gets up to leave, you can see the bust in greater detail. (00:26:55 - 00:29:10)
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Correction: We never see what sort of measures he uses to hide it until then, say a breakaway shed and "Authorized Personnel Only" signs.
dizzyd