Was Bob a Coffee Samaritan or an Electromagnetic Rube?

Last week, my friend and colleague Bob was driving home from work and he spotted a travel coffee mug balanced on the roof of the Xterra in front of him and Bob is a good dude, so when he came to stop at a busy intersection, he exited his car, jogged up to the driver, motioned him to roll down the window, and told him about the cup on the back of the car and asked if he should grab it for him, and the driver-- without making eye contact-- said, "Sure" and so Bob jogged to the back of the Xterra and tried to pull the cup off the hood, but it was oddly heavy and kind of sticky, but he persevered, got it off the roof, and handed it to the driver, who took it from him and said, "Thanks" -- but still no eye contact-- and then the driver stuck the cup to the outside of his door, a defiant and gravity-defying move that made Bob realize the the coffee cup was magnetic, seriously magnetic, and then, without further explanation, the guy drove off; Bob jogged back to his car, through heavy traffic, confused as to what just happened-- he wasn't sure if he rescued a coffee cup from the perils of the open road or if he had just fallen prey to a weird practical joke; a few minutes later he pulled up next to the Xterra-- and he knew it was the right car because there was a coffee mug stuck to the driver side door-- and the driver still wouldn't make eye contact with him and so the question still looms large in both of our troubled minds: was Bob a good Samaritan or a gullible rube . . . and if Bob was a gullible rube, then was the coffee-mug-bit a piece of hilarious prop comedy or was it the work of a true menace to society, who likes to see good dudes run through traffic so he can show off his magnet.