The app it wanted to install was its AOSP, it's likely that I was using another AOSP build at the time but I'm not sure. I've used either AOSP or gboard almost

The app it wanted to install was its AOSP, it's likely that I was using another AOSP build at the time but I'm not sure. I've used either AOSP or gboard almost all of the time, so it's 99% likely to have been one of those two.