Is it possible to have one roach in your house?
It is very unlikely that you would only have one roach in your house. First of all, where did the roach come from? It probably had a parent and siblings. Where are they? Roaches are expert hiders, and so it is not surprising that you wouldn’t have seen any roaches while they have been quietly breeding in your home. Then one day you notice one, but that one is just the tip of the iceberg.