I forget what the legal term for this is, but I learned about it in a business law class I took in college. The idea is that nobody recieves benefits for free. Anyway, if there is an iron-clad "honest to God" mistake made, where you supplied work or material to the wrong person, that person may have to pay you. There are factors like "is it reasonable that it happened that way", etc.. For example, suppose someone asked you to remove a $5000 pile or yard debris, and you mailed the contract back and forth - the papers are signed. But maybe you never went to the yard, or maybe an employee was sent. Suppose the yard next door also had an equivilent junk pile justly worth the same $5000 removal. Suppose both homes had their houses numbered with new numbers, but the number person swapped the house numbers. Suppose the houses were similar styles. Suppose nobody was home. That's hypothetical, but that's getting into the nature of this angle of law. If the wrong brush pile was removed - and nobody was home - then somebody will probably have to pay. Part of this kind of thing actually occuring, requires that somebody had to RECEIVE A BENEFIT. They had to receive something or some work absolutely worth the cost. Wish I could remember the legal name. But anyway, that's the deal. If someone has time for one of these short business law courses at a community college, you may find it worthwhile even if you only use 1 percent of what you learned.