In nature, ghost shrimp are just one step above plankton on the food chain. They are nature's "intended" food source for fish and fish do see them as such and in most cases, medium-to-large sized fish will view them as very tasty treats.
If you couple that with the fact that they are mass-bred in giant tanks and live in unclean and overcrowded living conditions with poor water quality until they reach your tanks, you have the recipe for a very short life span. Being a cichlid-keeper myself, 40-50 of them added once a week don't normally last longer than 5-10 minutes in my tank ... both because of the fact they are not hardy enough to endure subtle changes in their environment, and because my fish consider them a delicacy.
For whatever the reason, I'm sorry you lost your shrimp, Jen.