Thank you for your question.
The amount of stimulous check depends on the source of income and the adjusted gross income
Now two situations are exactly a like. Their adjusted gross income and source of other income may have been different than yours.
it is not that you are employed and retired, it is the source of the income and the adjusted gross income, and amount of tax liablity on your return.
This link provides a calculator which can help you to verify if your rebate was correctly calculated: http://www.irs.gov/app/espc/
This link is a list of specific scenarios. your particular scenario may not be listed: http://www.irs.gov/newsroom/article/0,,id=179165,00.html