Well I’d need to know the details. If the employee didn’t secure the lid properly and spilled it on him then it is their fault.
If the guy dropped it in his lap it’s his fault. If I go to a gun range and the range master lets people run in a shoot ganster style and rolling all over the place behind my back...and they shoot me in the leg. I’d sue the gun range.
You treat every firearm as if it's loaded. That's the rule.
Accordingly, you treat every coffee as if it's scalding hot and the lid is unsecured.