Generally, when people go on a medical leave of absence because of a non-work-related disability, their jobs are protected by the Family and Medical Leave Act (FMLA), which provides for 12 weeks of leave without pay (any pay has to come from the employer's sick leave plan, or short-term or long-term disability benefit plans). If the employee recovers within 12 weeks, he can return to his job (unless certain exceptions apply - i.e., it was a small employer of less than 50 employees, or the employee was so critical to the operation that he had to be replaced immediately).
Beyond 12 weeks, though, there isn't any federal job protection. Some States offer longer periods of medical leave, but as far as I know Texas isn't one of them. So once you went beyond 12 weeks on leave, your job was no longer protected by law, and they can legally replace you.
That said, some employers do allow people to return to work after longer periods, just because they have their own policies of doing so. It is, after all, generally a good business practice to let a fully-trained employee return to work, rather than have to find and train someone new. All you can do is ask, though.
Jeremy Bordelon is a licensed attorney in the State of Tennessee only, and is authorized to practice in all Tennessee State and Federal courts, and before the Social Security Administration in any jurisdiction. The answers provided on Avvo.com are for information purposes only, and should not be relied on as legal advice. This answer does not create an attorney-client relationship between us. In some jurisdictions, this answer may be construed as attorney advertising.