well i've got to say i've never even heard of a plant that both looks like and smells like bud but isn't. who knows man, you may have found some ancient extinct bud. lol i would take a samples of that and transplant them everywhere just in case that one is found. yea and if it does start to bud you've got to get some pics of it because that's got to be sum crazy psychedelic weed. : )
hey i noticed the crazy ass plant you came across, and its very possible that it is a marijuana plant. cannabis itself (as you said) is an extremely adaptable plant and if you couple that with all the chemicals, and other nonsense, the plant could have sped up the process of awakening dormant traits or simply mutated completely. Several types of plants have mutated into a new species completely when exposed to various "helpful" chemicals in short time (relatively speaking to evolution). Its believed that cannabis sativa (and the entire nightshade group) evolved from a distant relative of the spider plant which shares many of the properties you are explaining.
sorry for the long message but this specific case caught my attention and i had to find a reasonable explanation because only a dunce could confuse mj with another plant and these were odd symptoms.
hope i was of some help and thank you for sparking my curiosity (it doesn't happen often)