as title states, Little big planet is not locatable in Minecraft Store on Windows 10 or Android versions of Minecraft Bedrock Edition. you can not load the mashup page by either searching in the Minecraft store or by linking to the mashup from the Minecraft web page.

https://www.minecraft.net/en-us/pdp?id=4d7590d6-8f7f-4f53-989a-2df76b6b015b#

You can see every other product in the store (image 2) but Little big planet gives an error (image 1)

The major issue here is that I already own this pack, but I am unable to install it on my Windows 10 or Android. it is no longer listed in my Mashup Packs (image 3)

even using the direct link from the page above (image 4) you get the screen below (image 1)