Buried Treasure Maps turn into a normal Map when opened.

What I expected to happen was...:
I was going to get a treasure map that showed me where some buried treasure was.

What actually happened was...:
I got a normal map, it turned from a Buried Treasure Map to a Map.

Steps to Reproduce:
1. Find a treasure map
2. You get a normal map
3. ...
I found this treasure map except it wasn't opened for some reason but when I opened it, it was just a normal map, pretty sure it was the smallest possible map.