Cup a coffee

These cups are purchased at the local grocers and we use them when we want to take some coffee with us.
Yesterday I fixed one to take on the "dog walk" and when I took my first sip, there was no coffee.
I looked at the opening and it was closed - even with the little snap closure open. I tried to press it in with my thumb nail but no luck. L. loaned me his money clip which has a small knife included. I tried to punch it out with the blade. Still nothing.
Finally, I took it off the cup. The problem? Two lids nested together with the snap closure on the bottom one closed.
No spilling allowed but no sipping either.