*** I don't mean to sound like a moaner, but please try to use proper grammar, it's makes replying to posts a lot easier ***
It's likely that the cory has died from either disease, natural causes or toxic levels in your tank.
If you find a dead fish, immediately test your water, that's fish keeping 101!
If I could ask a few questions?
What size tank do you have?
How long has it been set up?
What is the stocking?
What are your water levels?