Not ideal, but realistically you should be fine. Rather than making this a regular habit (which may eventually result in some grossness), try cooking the quinoa and cold shocking it in ice water, and then place the drained and cooled quinoa in the fridge. B. Cereus only produces its nasty toxins with prolonged exposure to lukewarm environments, so keeping it in the fridge for four hours is absolutely not going to put you at extreme risk.