You must specify both seed and origin, otherwise I won’t be able to write anything about legendary location placement. I’m sure the location spawned on the map, you just didn’t find it, because the visibility of the Icy Cave is in the range of 80% of your general vision and can be further reduced depending on the terrain (forest, mountains).
On nexusmod there is a mod called “Find Grotesque Tree” (battlebrothers/mods/328). The second version reveals the placement of the Icy Cave by pressing Y.
