Monster Collection

Today I was trying Tangyoon's Kitchen to see what mobs I could get from it and somthing peculiar happen, out of all the mobs I killed just one was added and it was the snowman, I went to check in what set it was and found it nowhere not even in the "see all" but I saw a monster I know for sure I haven't killed had been added(Eliza being that one) so it makes me wonder if there are other mobs that are not in the collection that would trigger another to be added.

Edit: Scratch that, I got Eliza from dojo what I got was the snowman that appears at El Nath, so I guess the mob just needs the same name, it can look nothing alike and still be added.