I've had a variety of leaks, none of which produced puddles but all of which consumed oil steadily. The main seal leaking slowly drips oil when the engine is running, which cakes your oil pan and transmission with sludge. The CAS O-ring leaking (like wot mine is) leaks oil all over the heater hoses, which rot and begin leaking coolant. The camshalf seals leaking spreads oil inside the timing covers (I'm hoping mine aren't leaking).
Anyway, a lot of leaks only occur when the engine's running, because of pressure + moving parts. When you're driving, the oil is dispersed away from the leak location, hence no puddle and some issue with finding the leak!