Mary had gone up to Lending to find something she wanted to borrow for the weekend. She came back rather a lot non-plussed, having found it, eventually. It had been reclassified and put on the shelves.
Or, more accurately, a different class number was typed onto a spine label and slapped onto the item in question. Anyone trying to find it using the information in the catalogue record would have been fifty-four feet out.
We've only had an electronic catalogue for twenty years. It's not something we're used to yet.