Where have all the chipmunks gone?
We cannot say why you are not seeing chipmunks in your area. Wildlife populations tend to ebb and flow for many reasons which include lack of food sources, shelter, disease, weather conditions, etc.
See the link from DNR regarding chipmunks and their contact information http://extension.psu.edu/cumberland/news/2011/crop-rotation
Also, you may want to contact the Nuisance Wildlife Information Line at 1-877-463-6497 for more information. This service homeowners to receive guidance on nuisance, injured, or sick wildlife. This service is provided jointly by the MarylandDepartment of Natural Resources (DNR), Wildlife and Heritage Services, and USDA-APHIS.