Minimum wage works because it improves some workers' negotiation positions so that they can capture more of their job's economic surplus -- likewise, somebody sprung with surprise business travel, or surprise retail job responsibilities, is in a poor position to negotiate just compensation for this change in situation. So the presence of some sort of weakness of negotiation position might be what characterizes your generalized notion of wage theft. The minimum wage example is distinct from the others though because it doesn't spring any surprises on the employee.