Congratz! I sat around watching my first pregnant mother releasing her babies from her underside one evening when I was supposed to be going to class. They're near impossible to see with the human eye!
Out of 30 shrimps there's a good chance you've got a few males in there, which would lead to babies. Sometimes when you only get a handful of them, you'll pick out the reddest of the red shrimp and those will only be females. But perhaps they're hiding because of other fish in the tank? Bettas? Gourami? When I transferred my gourami out of my 15g all of the shrimps started hanging out in the water more. Though I do have some shrimps in my 30g, sometimes they'll be swimming out in the open.