For 4 days, the cat we are looking after has been in hiding, coming out to eat and eliminate-any suggestions?

The cat is used to living in an apartment, alone all day in totally quiet surroundings, with companionship only during the evenings and weekends. The owner told us that she is a reclusive cat and not very social. Here she is in a 3 storey house, filled with house sounds like laundry, vacuuming, forced air heating, people coming and going, radio etc. I am quite certain that she is hiding in our storage area, but I have no idea how to get her to come out, short of moving her food and water dish out of the basement and into the kitchen. Any insight would be appreciated.