I don't know what they were looking for, Ranger, since the later articles mentioned that the father and son stayed behind--and they had ample time to retrieve the money or anything else. And it sounds like the kid stayed long enough to pass off whatever was buried. And, since this was a gated community, I doubt that they'd have left anything buried for other culprits to retrieve.
In one of the pictures accompanying an article about this search (don't remember which one), I noticed the little "evidence" flags on the lawn. I don't remember whether they were on the front or back lawn, but I'll try to find the picture later.
Since he claimed to be an engineer, and BL's father built prolifically in SA, and Jeddah was where he was headquartered, I'm wondering if this guy works for OBL's family?
It's also possible that he had blueprints of the WTC or worked with some cutout doing some form of engineering work for the complex--and perhaps gathered engineering intelligence about it.