not to be in anyone's defense, but in my experience, these things are pretty hardy. I have seen mangrove "pods" (I am not a botanist) stay in the heat of the sun on pavement for weeks and then go in water and begin to root, and shoot off their first leaves. I have also seen them stay on the sand in our winters (sometimes 4- 5 days (evenings) of 30 degrees F, and in the Spring, they begin to root.
I am not saying that the ones on ebay would fair as well. Just make sure you find out if they are rooted and already growing, otherwise you'll be in for a surprise, as I have had only a 33% success rate of getting un-rooted ones to sprout.
I live in FL, and I have grabbed literally hundreds of these at a time, and placed them in my refugium. For the ones with no roots/leaves: if you don't start to see roots in the first 2 weeks, it is my experience that you can forget about them. However, if you start off with roots and/or top leaves you have more like 80% chance success/survival.
They live in brackish water here (about 1.021) so I slowly get them used to the 1.025 my tank/ref is at.
Hope that helps