You should speak with an employment law attorney. As a general matter, if you did not have an employment contract, an employer may terminate you at any time, for any reason, and is not required to tell you the actual reason. Furthermore, as a general matter, an employer may terminate person A to "save costs" then decide it needs someone in that position and hire person B. However, there are some exceptions to the above:1) If your medical condition would have qualified as a disability, which means that it had a pervasive impact on basic life functions, you may not be discriminated against in employment due to it.2) If you used FMLA leave, or leave under a similar state law, you may not suffer retaliation for so doing.3) If you are over 40 and you are being replaced by someone younger and less expensive in order to save costs, that could be age-related discrimination.Therefore, depending on the exact circumstances, there are several possible grounds for a legal claim; therefore, it would be worthwhile to consult with an employment law attorney. Good luck.