which hen laid the egg!? help???

Does one of them exhibit signs of readiness to lay? Are they the same age?
If one of them is "squatting" when you come near or reach for her, but the other is not. . .the squatter is probably your layer.
Does one of them have a redder comb and wattles? She may be the egglayer.
You can also check the vent. The vent of a layer is larger, and moist-appearing. It looks different from a nonlayer, so by comparing them you may be able to figure it out.
There is also a way to tell based on how many fingers across you can place between the pelvic bones on the chickens rear end. Further apart may mean layer.
I hope some of this helps.

 

Go out tonight with a Q-tip and two different colored bottles of food coloring.

Paint both of their vents different colors.

Watch to see what color gets smeared on the eggs. That's your layer.