Sands of Time Book 4 question

Sean David MortonI've noticed that there is a book missing from Sean David Morton's Sands of Time book series, namely the 5th book or the sequel to Sands of Time Book 4: Time Runner - Act One. Funnily enough it is also missing from Amazon, even though I bought the book there. This is where you can buy it at Sean's Website: Strange Universe Radio dot com It really does exist. I just don't know how to add it. Thanks for your help on this.