When I create on the moon there's a bug where my creation suddenly disappears while I'm creating.

I think I know what you mean. Sometimes after changing some edges of my object, the object itself cant be selected anymore. When I press 'Undo' it completely disappears. I experienced this bug two times at single objects only.

I dont know what exactly causes this object to disappear, but it's a strange bug. Simply press 'undo' when the object cant be selected anymore and try to restore it. Thats all I can say.

I know this bug while working with rail. If the rail is to complex and goes inbetween layers, imidiatly after picking it with popit it will selfdestruckt. It happens only if you pick a new spot in the curve which goes from layer to layer. The new created spot is not in regular place and the engine try to place it properly. Since every spot is in its own unique depth, there is no proper depth for the whole construct.

Other possible reason is when object is placed in the other object and you try to move it.
It doesent matter if both objects are static because you are moving it.
In the LBP2 i used the rope glitch to move objects freely around with no clipping.
As soon as placed, its best to glue it.

Perhaps this will help.
Have fun.

I believe I came up with the solution. When the object cannot be selected, you'll just need to return to pod. (This won't make object disappear when you undo). Also parts of level can just disappear if you use dynamic thermometer. (It just bug from code)

I had this bug two times and I personally always pressed undo and created the object again.