Sorry to hear you got stiffed. Trust is earned, not given these days. Hate to say it, but that way seems to be going. Personal policy for doing work on the side has been: Contract first time, looser next to see if they try to be slippery. Verbal only for known honest / repeats.
After this happened to me once, my driver's instructions were "Get check before unloading". Sure some people get pissed but you can always talk then down on the phone...
