[[Reconstruction:Proto-Indo-European/h₁eyH-]]
Creating categories isn't my area of interest, but until that category is created, there's no point in putting that template there. If you're trying to encourage page creation, create a category like Category:Latin nouns with red links in their declension tables.
Do you think that whoever will create the category will think to add the template back in?
No. All root pages should have {{PIE root see}}
even if the category doesn't exist, just as all suffixes should have {{suffixsee}}
.
That seems odd to me, but if that is the case, would you be opposed to having the module hide the "category not found" message if it doesn't exist?
Then create a category like Category:Latin nouns with red links in their declension tables; "category not found" messages simply look silly.