Yes you could have a leak... first was the engine teperature the same both times?

Coolant leaks can be anywhere- examine the engine closely- look for corrosion/splits/cracks around all the hoses. Look on the ground where you park- any wetness? In extreme cases the leak can be internal. Look closely at the oil... is it whiteish- could coolant be mixing in with the oil?

Look at the exhaust- are you noticing an unusual odor or color, or more water vapor than usual? Could then be a head gasket leaking coolant into the combustion system.

If you find no evidence of leak- refill the system and carefully note the level while engine is hot. Re-check frequently and see if it goed down- look also for a clue as to when it goes down--- after a long hard run, or after sitting for a while?

Carry a spare container of at least a gallon of coolant in case something lets go during a trip. Watch your engine temperature gage for creeping temperatures.

Let us know hwat you see.