The house guests could have caused emotional distress to cause the problem. However, if this is the first time this cat has done this you need to rule out medical problems that may cause inappropriate urination.
Have your veterinarian do an exam and lab work (including a urinalysis). If medical problems are ruled out the behavior may resolve once the house gets back to normal. However, it is important to adequately get rid of the odor. Two products effective in this regard are Feline Odor Neutralizer and Urine Off.
Some medical treatment may be required to address the stress. One of the most effective treatments for this is amitriptylline. Alternatively, short term hormonal therapy may be helpful. Make sure you discuss potential risks of such treatments with your veterinarian.