Jim O'Donnell was at a library conference in Singapore when his Ipad's Google Play app asked him to update it. This was the app through which he had bought 30 to 40 ebooks, and after the app had updated, it started to re-download them. However, Singapore is not one of the countries where the Google Play bookstore is active, so it stopped downloading and told him he was no longer entitled to his books.
It's an odd confluence of travel, updates, and location-checking, but it points out just how totally, irretrievably broken the idea of DRM and region-controls for ebooks is.
But all of my books had un-downloaded and needed to be downloaded again. The app is an inefficient downloader, almost as bad as the New Yorker app, so I dreaded this, but clicked on the two I needed most at once. (I checked the amount of storage used, and indeed the files really have gone off my tablet.)
And it balked. It turns out that because I am not in a country where Google Books is an approved enterprise (which encompasses most of the countries on the planet), I cannot download. Local wisdom among the wizards here speculates that the undownloading occurred when the update noted that I was outside the US borders and so intervened.
Atypically, Google has Google Play help service available by email, but a series of exchanges demonstrated that the droids at the Android Store were neither able to comprehend my issue, sympathize with my plight, or offer a remedy. I must return to the US to be allowed to spend a few hours redownloading "my" books before I can read them again. At one point they asked what features I might suggest be added to Google Play. I suggested "Don't Be Evil", but got no response.