For comparison, the furthest we've dug down is about 8 miles, and Europa's ice crust is estimated to be 10-15 miles. So, yeah that would be like us getting discovered by mole people from nearly twice the depth we're capable of reaching. It's fun to think about what a civilization on Europa would think about their world. You can go up, but it gets colder and the pressure gets lower. It'd be like trying to go to space, but you have to dig to get there. Perhaps the change in density would make any such upward drilling unstable and beyond their means.