Guy,
I have intentionally done what you experienced to make a
panino, using regular pizza dough. I saw a chef by the name of Roberto Donna do this to make a
panino on a Julia Child PBS segment (the dough and
panino recipe can be found in Julia Child's cookbook
In Julia's Kitchen with Master Chefs). To make the
panino, you take a piece of dough sufficient to make an 8-9 inch pizza, form it into a skin as you would to make a pizza, and put it on a pizza stone that has been preheated at 500-550 degrees F. When the pizza dough balloons up and starts to turn a light brown (you have to be careful here that you don't let the dough overbake and become cracker-like), you remove it from the oven and immediately start cutting the baked dough around the perimeter (preferably with a serrated knife) to separate the baked dough into two halves. You then fill one half with things like mesclun or mixed salad greens, olive oil and balsamic vinegar (which are mixed into the greens), thin slices of mozzarella cheese and thin slices of mortadella or prosciutto, and finish with salt and pepper. Cover with the other half of the baked dough and press down gently to flatten a bit, and cut the
panino into quarters. Not only does it make a great sandwich but it impresses the heck out of people when they see you make it--especially the part where the pizza dough balloons up like a small basketball

.
Peter