2015 Prius brief brake failure

I was in a drive through that had a slight incline - for 3 seconds my brakes felt normal but the car didn’t respond and I started slowly rolling back. I noticed that when I tried the e brake it didn’t show on the dash or work. After that I hit the brakes again and it stopped. They seemed to work completely fine after that, after a couple of tests on a side street. It didn’t feel like the usual short brake slips when you hit a bump while braking. Not sure if it’s necessary information but I was driving for 30 minutes tops- and it’s more humid than normal for my place of living. Any ideas what could cause this? Can I safely drive it for now?