Hi Zach,
You won't be able to miss the eggs. They are not too small, really, and hang down like Christmas ornaments. Besides, the mother will be climbing onto sturdier things to plant her eggs, like caves and filter pipes and such. If she doesn't find anything else, she will take "grass" too, I guess, but mostly she will be looking for something she can grasp.
Edit: Guess that didn't answer your quesiton, though, did it. I would suggest Java fern. It looks sort of grassy and has nice broad leaves for suspending eggs. It shouldn't be put right onto the sand, though, but onto a rock or some other more porous base. Valesneria looks just like grass and grows in the sand, but I have had mixed success with it in my tanks.
-Eva