Agreed, but plugging in things simply because they fit is a very bad practice, unless you suddenly remember you removed that plug yourself and forgot to plug it back in. In the other case, you will need to check a cabling diagram or ask someone with similar hardware to find out where the plug should go. Trial and error can cause permanent damage. In your case, it turned out fine.
This brings us to the question if you bought the unit in "working order" or as defective? While a fan might go bad due to transportation, and maybe the thermal pad might crack, the odds of a plug becoming lose as well is pretty low, unless indeed that plug comes lose with little or no effort.