#21: The crying of Lot 13

In the bitterly cold, dark Helsinki I visited a museum briefly, just before the closing time. The lady at the counter said I could enter for free and that I hadn't much time. We had a small chat. Among other things the lady mentioned that she lived in a flat #13.

The exhibition brought into being a world bygone, a 1950s Helsinki of greased-up hair style and wooden house quarter labyrinths.

When I was leaving and putting my coat on, I became aware of one locker key missing. What is this? A plot with a hidden message to be communicated to me? Like the mysterious postal mail Trystero in Thomas Pynchon's novella?

All of a sudden the lady came, put a small box in and left. What was there? Inverarity's stamps?