However small fish are amazingly resilient. If she shows no bruise or internal bleeding and behaves normally, she is probably ok.
How long have you had this female? When was she with males either in a SHOP OR IN YOUR AQUARIUM?
Also, what temperature is your aquarium set at? That 28-30 days thing assumes a certain temperature of maybe 25-27 degrees F. It varies by species but each species will flat out stop dropping fry at a certain temperature.
I want to say that my Endler's livebearers (either Poecilia wingii or just a guppy strain) didn't drop any fry ALL WINTER the year my fishroom was 70 degrees.
Equally important, what companion fish do you have with the female guppy. Are you sure the fry weren't just eaten?
What hiding places are within the aquarium? Is a power filter sucking the fry out? :(
Please take a look at Immediate Help (the link is to the upper right of this page) and read through the section on pretecting fry.
I look forward to your description of your aquarium.
All the best!