Mysterious Sprout?

So, I checked on my plants today (23 days old) and saw a little sprout beside one of my larger ones. I pulled it out, as I wans't sure what it was. There were no extra seeds, and it was in a soil-less mix that had been kept frozen before use. I'm thinking now that one of my plants may have cloned themselves? Is this possible?

some soil mix's have weed seeds (not marijuana) in the mix. that sprout similiar to Marijuana. i had one pop out of my soil at 4weeks veg randomly. it looked like marijauna so i let it grow, but it grew weird shit instead of marijuana true leafs,

if its marijuana, thew only possibilty is if it dropped seeds, and one germed and popped. its impossible for a plant to clone itself.