It changes every week

Most likely its there next week :)

Do you see the information icon just above the first item (silver) that says "ITEM POOL?".  Click that and it will tell you what might be in each slot each rotation.

Just what folks above have said. The available items in the slots change on weekly basis. You can get full info about items that have a chance to appear in a particular slot through the information icon at the top of the screen.

 Interesting, I have the exact same options available in my clan shop. I thought it was random chance but this looks like it might actually be a fixed rotation. I like the energy and rare books but the accessories are the best value, after I develop my account a little more I'll definitely start collecting Yannica fragments.

2 weekly cycle, itll be back next week 

rare books are cheap as too the silver if you have a few tokens stocked up but most i believe are hauding the counter attack accessories

It is indeed the same for everyone.  I remember them saying this on launch, as I think they wanted it to be fair for all. 

Also, it's not a rotation, it's a random chance.  For example, slot 2 has a chance for energy and 3 star chicken.  Each week it seems to roll it, and it is 100% possible to get the 3 star chicken 2 weeks in a row.  I know this because it happened during one of the fragment events and I was relying on getting the energy from there to finish some tournaments.  Ended up using gems

So there's no guarantee that there will be energy back in slot 2 next week

I don't think the rotation is 'fixed' but it is the same for all players according to the news.  So, no telling what it might be next week, but it will be the same for everyone.