Carolina, here's a great tip for when you need to extinguish a bowl you plan on returning to. Wine bottle cork. I cut them in half so they're not as long and don't stick up so high off the top of the pipe bowl. You may need to shave one end down a bit to better fit your pipe's chamber. Or you may need a larger cork for larger chambered pipes. But I carry one with me when out and about, and if I need to stop smoking, I simply squeeze the cork into the bowl and the embers go out. Also, they don't stick too far down into the bowl, so I'm not overly tamping down my tobacco or tightening the pack too much. When you're ready to return to your smoke, remove the cork, light up, good to go.
Edit to add: And if you get bumped, the tobacco ashes won't get knocked out and spill into your pocket.
Edit to add: And if you get bumped, the tobacco ashes won't get knocked out and spill into your pocket.