terraform and painting trouble

Working with the 2.6 i have modified my terrain and plant some flowers and tree on it with painting…I have saved my scene and my project playing my scene and…after I close the soft unity 3d and re openend few minutes later … and all my work : terraform and painting have disappeared I 'm like at the begining …I restart the modifications, save my scene and my project, build and run, close the soft and re open it and …no modifictions
… What is wrong … Am i alone or some one else got this strange trouble and what’s the solution…
I degrade to the 2.5 version because with this version i have no problem …

When you open the project, is it coming up with a blank scene, or is it just the terrain object that is being lost?

I can see my terrain but i have no modifcations done before on it.
I have tried to create a new projet and a new terrain with terraform and vegetation and it works very well.
It seems that I have a problem with this kind of terrain … i have use the multiplay island demo project to build my own…

In fact after checking my project my terrain was not imported in the 2.6… I can see the terrain but the terrain asset was not in the project … incredible but true…
So I opened again my project in 2.5 reimported my terrain asset and its dependencies, saved the project and opened it in the 2.6 …
Now I can do a normal terraform and vegetation painting and all my modifications are saved in the scene when i re openit …
ouf !!! (in french)