It would seem you're saying some guy is using the body of his truck as an antenna for wifi? So, basically, he's got a piece of coax attached to the body of his truck and he's picking up signals.
If this is true, then he's also greatly increased the SWR (Standing Wave Ratio) into his card. If he continues to do this, his card will eventually die. As a SWR of 3.0 or greater on any RF transmitter is fatal. There would be no way he could possibly tune the connection to get the SWR within acceptable parameters.
If you're using the antenna in the link, continue to use it, it looked like a decent one.