My question is: why did you mention the spill to an employee?
I think by telling the employee about the spill, you were acting like you thought it was an emergency, when - to the employee - it was not.
Sort of like saying: "Sir! My son just dropped a fry on the floor. Can you come and clean it up?"
It was still not right to offer you a mop, but I bet the employee was thinking: "calm down, lady...it's just a spilled soda...help yourself to the mop if it is stressing you out that much".
One reason that many people have never grabbed a mop in a restaurant like that is because they have never gotten into a conversation with employees that could go that far!
I think, next time a soda spills, just grab some napkins and dry the spill to your comfort level - it's nice to not leave too much mess as a customer - but, beyond that, know that the staff are busy but will mop the floor at their regularly scheduled time.
The only time you need to jump up and talk to an employee is for an *emergency*, like if a glass breaks and then the broken glass could be dangerous.