If the search and seizure by law enforcement is determined by a court of law to be improper, then that evidence that was gathered and the fact that they searched you is not admissible to the trier fact, generally a jury or a judge. For instance, if they found an illegal gun in your car, the government can never use the fact that an illegal gun was found in your car so they could never convict you. Again with a drug offense, if they found illegal drugs then they could not use that evidence against you. The chances of success in the prosecution without the main piece of evidence is very minimal.