Braking issue

[Zircon65]

Hi all thanks for allowing me to join the site, the brake pedal on my 2013seat Ibiza toca suddenly went to the floor as I was braking with no warning.I,ve cleaned and adjusted rear shoes and checked everywhere for leaks but nothing,the brakes are fine now but I,m very wary of using the car in case the same happens again. I’ve driven the car a few miles locally and brakes are fine but I,m afraid to do any long journeys in it, the servo is working fine and fluid level hasn’t gone down any help would be appreciated. Thanks in advance.