Occasionally, I will hear someone say that he/she searched for their invention at the patent office, but there is nothing like it. But, more searching is likely needed. It is almost never the case that there is nothing similar to a new invention. New inventions are built on the backs of prior products, inventions, and/or knowledge.
Usually the problem is either that the person (a) has not searched in the right place or (b) is too narrowly viewing what is similar. When someone hires a patent search to be performed, the search almost always finds something related to the invention.
If a search is coming up with no results, then the patent search must be broadened. The search can be broadened by looking in different classifications or by searching for different keywords. Broadening the search can include searching other technical areas. In evaluating the patentability of an invention the patent office sometimes looks to references that are not in the same technical area as the invention but that are directed to the same type of problem that the current inventor faced in developing his/her invention. Therefore you might ask what other technical areas might address the problem or problem(s) you sought to overcome by your invention.
While relevant or similar results exist for almost every invention, those results do not necessarily block an invention from patenting. Interpreting the results is what patent attorneys do to advise their clients on the chances of obtaining a patent.