Realized on last viewing...
...how improbable it was that she found herself in Renato's store, with Mauro's unintentional guidance, after seeing Renato at the Piazza San Marco, and that she would buy the same style goblet that her acquaintance did, and that that acquaintance would show up with her glassware just as Renato was present, and that she would insist on showing Jane the glassware in his presence.
Obvious story devices, but they work; people accept the story.
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