The cotyledon leaves are far too round for it to be cannabis also why would another plant show up if you only planted one seed and that plant is far way mature destroy it as it will use any nutrients that can be given the cannabis plant instead.
I like to direct plant for this reason leaves less exposure then pots but the soil in my sites is so built up its just perfect. Another good idea is to have multiple sites so even if one gets ripped there's a good chance you will still have some insurance of having a harvest also it's not to...