As you mentioned, rats have an excellent sense of smell. They also have poor eyesight, so do with that information what you will. They're very intelligent and are very cautious of new things, so a lot of trapping videos suggest feeding them for several days on a train with the trap not set so that they'll become comfortable enough that they won't know what hit them on trap day. In your case since you want to be humane, maybe try making a bucket trap with a hinged piece of plywood and a tall bucket, and secure the hinge on the lid for a few days while you put food there to habituate it. Then let the lid swing freely and there's a better chance you'll get it. But use a tall bucket or even a garbage can, because as you saw, those little buggers can jump!