The OP mentions that it was a scroll of power. Presumably, it was labelled "irk gleknow mizk" in its unidentified state? Scrolls labelled as such are always given this tile presuming they will be IBM guild manuals. Sometimes they aren't manuals at all, making this tile just... wrong, for them.
Then again, if the scroll at the heart of this issue wasn't labelled "irk gleknow mizk" and was created with a book tile for some other strange reason, that would be a stranger bug...