If you find one maggot in your house does that mean there's a bunch more you haven't found yet?

Maybe, maybe not. It is fairly likely that what you saw was not a maggot (fly larva) but rather the larva of a 'pantry moth', or Indian Meal Moth, which infests dried foods in the pantry, everything from chili powder to flour.

The larva can get into closed jars, ziploc bags, and tupperware-type storage containers; and generally has slight webbing around it.

Eradication requires removal of all infested foods, perhaps baited glue/pheromone traps available at some grocery and hardware stores, and thorough cleaning of all nooks and crannies in the infested area (perhaps including underneath cabinets, behind refrigerator, etc.) .

Prevention of re-infestation is aided by freezing dry goods for 48 hours before putting in cupboards (to kill any possible larvae in the new food), rearranging of cupboards (the moths like a settled locale).

See related links below for more info and brands of moth traps.