Did you not see any coolant/overheating light come on? ... Or engine check light?
This is going to be low coolant/holed radiator
Pump belt or pump impellor failed
They can't tell you it is wrecked (it may not be) ... as you are still driving it same day and they haven't stripped it to check.
Don't make it worse by continuing to drive it. Water may be getting into the cylinders and will cause rapid erosion and wear of the rings/piston(s) (as steam) with no lubrication .. as will be washed away.