This is definitely a bug with the Nook Touch losing track of the SD card. In the middle of filming our
Nook Touch video review, all books on the microSD card miraculously disappeared. I was about to tap on a book in PDF format to show PDF handling and it was gone (along with all other books on the card). When this happens, I remove the card and re-insert it and it comes back.
Happily, I haven't had problems with it losing last read position in side-loaded books, but I do always exit to the home screen before connecting USB.
I've also noticed that if I use a card reader to side-load books, then insert the card, I get random errors like "can't read that book". A reboot fixes that.
- Lisa