You have no other option then trimming it and gently push it back onto the substrate.
I believe there is a Tom Bar video roaming the net where he shows this with HC.. But i can't seem to find it back.
Preventing it from lifting, is keep trimming it on time. That's the most difficult point with growing carpets from this type of plant. You need to trim/destroy it when it looks at its best. Thus it's enjoying the great looks for a week, then trim it back, wait for it to look great again and so on and on, back and forth. Till you want no more..
Yes, of course, it can be saved you have healthy plant mass enough to plant back into empty spots.
It's hard to describe in words how far you actually should trim it back. All that is not rooted in the substrate will all surface anyway if you start trimming. How it finally looks bellow that when you are done remains to be seen. I can't say upfront from a picture. But i guess it will look pretty bold. Then just put back into the substrate where needed.
Watch some videos on youtube about trimming Glosso, there are quite a lot about it. That can give you an idea of how to go about.
You might do some test areas
- trimmed as usual (the main area)
- trimmed back to substrate
- “pads” cut out and replanted (just plant back 10-20% as it should fill in quickly)
You should see in a couple weeks which method you prefer
Depending how long you want to maintain this scape, I’d be inclined to lift the lot and replant, this time focus on frequent trims to form a tight dense carpet
Im going to trim it back quiet a lot and push down the roots it only apears yo not be planted in one lil area so il see how it goes if not successful il take up and replant which wont be to much of a heart ache there is plenty of it to use lol
I would take the other route of lifting the areas that are no longer in the substrate and replanting the healthy Glosso! trouble with triming it is you will be trimming back the healthy growing part of the plant which should ttake very quick when replanted, Plus when the substrate is exposed its a great time to vacuum it so win win IMO and glosso does grow back very quick, I sometimes butcher mine when trimming and it still bounces back.