You prob got away with it. The exact same thing happened to me the other day, GT was up on my ramp at work and left it running. And seen coolant starting to bubble out the overflow after about 10 mins. Fan wasnt kicking in... Anyway for the meantime i've taken out the fan relay, wired the + to the 12v ign slot and earthed the - to the earth point next to the AC relays. Means the fan comes on with the ign, might reduce fuel economy a wee bit. But my plan is to wire an in car fan switch into the hi/lo boost button as its not used anyway.