These guys disappeared between 8:55 A.M.-1:50 P.M., so broad daylight. I say no way anything actually happened in that lot.
So if something bad did happen to them, maybe it happened elsewhere and the truck was just dropped off at this location? And maybe there was evidence in the truck that something had happened which caused the quick action with the missing person notifications. If its used pretty often, nobody would think anything of someone dropping it off, and getting in a vehicle with someone else. Just my opinion, as of right now.