My host came with a mongodb instance and there is no /db directory so now I am wondering what I can do to find out where the data is actually being stored.
While this question is targeted for Linux/Unix instances of Mongo, it's one of the first search results regardless of the operating system used, so for future Windows users that find this:
If MongoDB is set up as a Windows Service in the default manner, you can usually find it by looking at the 'Path to executable' entry in the MongoDB Service's Properties: