[btrettel]

Once when I was visiting a technical library, I saw that they had many volumes of a particular 1940s Russian engineering journal (Izvestiia Akademii nauk SSSR, Otdelenie tekhnicheskikh nauk, rare in the US, probably common in Russian) that had several articles I was trying to find copies of. I opened the index to the journal from the early 1950s to determine the volumes to check, and must have found that they didn't have the right volumes. So I put the index in the reshelving spot.

A few days later I saw the index in the free book pile. I took it and showed the librarian on duty. As I recall they said that the journal wasn't in the online catalog, so they didn't think the book was theirs (despite the markings on the book clearly saying it was). They seemed quite alarmed that they nearly threw out the index. I imagine the journal is now in the online catalog.

Later, I scanned the entire index just in case it disappears for similar reasons in the future...