Houston, We Erased The Apollo 11 Tapes
An exhaustive, three-year search for some tapes that contained the original footage of the Apollo 11 moonwalk has concluded that they were probably destroyed during a period when NASA was erasing old magnetic tapes and reusing them to record satellite data.
There is the saying, "If we can go to the moon we should be able to......" that ends with what you want to be able to do but cannot, can now be modified for libraries:
"If we can lose the moon landing tapes we can lose anything."
Story at NPR about the loss of the moon landing tapes and a mention of how a second copy offered some hope but in the end did not pan out.