The moistened vermiculite within the sealed baggie should make it an enclosed system, and the moisture should stay at a decent level. Once you insert the pieces of the bulb into the vermiculite inside the baggie, zip it almost closed... blow into the baggie to inflate it, and seal it the rest of the way. That should create a bubble, sort of like a small terrarium.

The Emerald pieces I cut up and bagged in moist vermiculite are still moist... I haven't opened the baggies since I sealed them. The baggies form condensation on their insides from sitting on the buffered tray which is on a heating pad for plants. Tapping the baggies makes the condensation drop back into the vermiculite.

A couple of the pieces I bagged look like they're dying, but a couple of others still are alive, having white flesh. I haven't disturbed them in quite a while, but I did think I saw some type of growth happening in one of the baggies. I'll look closer later today and photograph it... if there's something worth photographing.

Here is an update to my attempt to salvage something from Estella.

See the link below for the status as of mid-July.

I took another look last weekend. The one with the larger leaf had grown enough to reach the top of the bag.
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Not having any better ideas, I decided to move the piece into a pot of its own. I took a look at it out of the bag.
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As you can see in the close-up, there are no roots.
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I put the piece into a pot with vermiculite, thinking that it might be happier if I did not change the medium until it grew roots.
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As an afterthought, I put the pot into a larger 1-gallon zip-locked bag. The other two pieces are still in the 1-quart zip-locked bag. They are still alive. So I wait.

Here is a link that might be useful: Maybe I'm Amazed - Estella

Have you introduced your potted one to some light? I would assume the tiny sprout needs light to make some food on its own as suppose to continue to consume the reserve from the mother's fragment.

-GM

I'm going to have to attempt this with Grand Cru this year. I think it was on its way out when I bought it. Ugh. I'm so glad you are here to teach me, Jodi :-)