The first option: without the chemical trail to go back home, the worker ant is doomed. It could eat and survive on its own, sure, but why? It lost its purpose in life. It cannot reproduce or start a new colony. It will keep walking until it finds its nest or dies ... and the latter is very likely. An ant protected by other ants, especially soldiers, is one of an army. An ant by itself is a light snack. Also, if the night is too cold, the ant will freeze without the relative warmth of the nest.
What if it meets another colony of the same species? It depends: sometimes it will get lucky and be accepted, but more likely it will be killed. Each colony has a unique "passport pheromone" on all ants in the nest, allowing the ants to smell if another ant is family or an invader. Whether these pheromones are nest- or just species-specific likely varies among the ant world.More questions on Insects: