It's the bane of my life - and probably that of every other economist who (tries to) work(s) with time-series data. Historical data that simply disappear.
Shazam! Now you see, it; now you don't!
You know the sort of thing I mean, I'm sure. Just when you think you have a nice long, consistent, series of economic data, the statistical agency in question suddenly stops recording it. They change the basis on which the data are gathered (usually for perfectly good reasons), and leave you with a big red DISCONTINUED descriptor.
Gee - thanks a lot!
Sometimes they even "pull" the historical series that you were really counting on, and just provide you with a pretty new series that started yesterday, and won't be of any use to anyone for ages.