Okay, so micro-lobsters have their reproductive organs behind their eyes, not where shrimp have them, what we thought were ovaries is a poop chute, that's good to hear.
At least now you know that the reproductive organs are behind their eyes, a good place to try to check with a flashlight and magnifying glass.
Eggs would be a tell-tale sign.
Did you ask them what differences they did notice between males and females? It only says that they had trouble distinguishing between them, and doesn't go on to reveal the differences they did notice.
The claws on the males and females are VERY distinguishable, they're not the same in both sexes. Check out a group picture of Opae Ula and you'll see different claws, and stated before the tip and underside of the tail is different also.
We can't check the swimmerets without harming the shrimp, so that method rules out.