I have a mushroom as you described. They were a server birth originally, but there was a way a long time ago to pick them up.
Unfortunately, there was a bugged way to get them before the heartwood mushrooms became blessed. This bug to the best of my knowledge no longer works as they are now blessed. (This is when we saw folks selling them in luna). Good thing is I don't believe any more can be made. Bad news is that I'm sure it has affected the value of the server birth variety, but I do believe since we still are not seeing them sold in Luna - there weren't a lot that were made.
You can see my mushroom on Atlantic on the roof at Dragonstorm Manor - just outside of southeast bridge of Umbra. There is a teleporter to the roof on the first floor - all the way down the hall and to the left.