It may be legal:

1) FMLA only applies to companies over a certain size--I think the threshold is 50 employees, all within a 75-mile radius . So if your employer was smaller than that, it would not help you.

2) You need to meet certain threshholds of hours worked and how long you worked there to be eligible.

3) An employee has to indicate that (s)he is taking FMLA leave--they have to do that in advance, or at least at the time of, the leave beginning. They cannot simply take time out then retroactively call it FMLA leave. So if you did not inform your company, then even if they are bound by the law, they may not need to honor your leave.

Here's a link to a FAQ sheet you may find helpful: http://www.dol.gov/esa/whd/regs/compliance/whdfs28.pdf