Inside the basement of the Capitol Post building located in L'Enfant Plaza, there is a corpse named "Gibson". Gibson's inventory has four items, two of which are "Gibson's Key" and "Gibson's Scrap of Paper". The scrap of paper has the following message, "Search the house!"

This references an early scene in Snatcher where the player finds Jean Jack Gibson's corpse and discovers a key and a scrap of paper with the "Search the house!" message among his belongings.