Once again, this is not true. They do what is called a prior art search as part of issuing a patent. They look worldwide for anything that could be considered your invention before your filing date before issuing a patent. Even after a patent is issued, if prior art is presented to the patent office they can rescind the patent. It’s a form and like $100. You don’t need a lawyer to bring prior art to the patent office’s attention. The legal battle will be between the patent office and the patent troll if they are trying to contest the prior art.