In the quest "Imperial Cult: An Unlikely Convert", Misinath Ulvam asks the player to either get his book back from the guards or get him a new copy (the only option atm), but the guards in Tel Gilan currently even can't be asked about the book.

At this point the player should probably be able to ask the guards about the book, through the topic "For my Gods and Emperor"

I think it could be easily implemented as a dead end, with the guards just saying they got rid of it, or them saying he shouldn't be worshiping the imperial gods in the first place and not elaborating on the book any further