Your employer is not required to keep your job open while you are getting workers compensation. You can be fired or laid off. This can happen in some cases where work restrictions are preventing you from going back to work for several months. Many employers will try to keep your job available, but at some point, they may need to bring in someone else.
It is helpful for your cause if you communicate regularly with your employer while you are off work. If you do that, it is more likely they will hold your job for you. Make sure you keep the company informed about your health situation and when you can return to work.
Also, if you do come back to work, you are not assured an exact job or pay rate.
But you cannot be fired for claiming workers compensation. This is illegal and you can get more compensation in this case, above and beyond what you are entitled to for workers compensation.