I think my friends game is glitched...or are we missing something?

I finished this game pretty quickly after it came out so I haven't played it in forever. My friend and I decided to play it yesterday so she could finish it. We both had to dl an update and started playing on her game save. We are as far as building the Keep in the forest world and now he is telling us to go find the princess. We are missing the piece of the archway to get to the Desert Kingdom which I know is where she is. We have done everything we can in the Ice Kingdom and the Forest Kingdom, as far as I know. We built the University but we need 2 books to activate it and we have harvested everything there and can't find the books. I can't remember where we get the books anyways. Basically we are stuck and I don't know if the game is glitched or we are missing something. Where do we get the piece we need to unlock the Desert Kingdom?

The princess is probably hiding in a building. It's easy to get stuck at this part if you skipped the quest to find her. Try knocking on a few of the buildings to see if she pops out.

Yeah we figured that out yesterday after we started the game completely over. Got to the same part and she was still missing. Tapped on all the bldgs. and out she came. I kicked her for a good 5 minutes.