Millions of objects are being connected to provide different services via the Web. This trend has led the paradigm of Web of Things (WoT), that can be searched and leveraged by uses (i.e., human or other systems/machines). One of the key enabling technologies for materialising the WoT vision are search engines, which need to be highly sophisticated pieces of complex software systems. Researchers and practitioners have been allocated huge amount of resources for developing a large variety of search engines for WoT. It is pertinent to critically review the state of the art on search engines for WoT to assess the currently available search engines as well as to guide the future research and innovation efforts in this area. To this goal, we have recently completed a large scale review of the search engines for WoT. We are ver proud to share that our review titled, Searching the Web of Things: State of the Art, Challenges and Solutions, has been accepted in the top quality journal ACM Computing Survey. Here is the preprint version of the paper that provides a detailed critical review of more than 30 systems and highlights the open issues that need to be addressed in order to achieve a so-called ideal WoT Search Engine.