Last modified: 2013-05-22 13:03:26 UTC
If you create a property page and then delete it, it will still show up in the pages Special:Properties and Special:UnusedProperties - it shouldn't. And similarly, it shouldn't be returned by smwfGetStore()->getPropertiesSpecial() or smwfGetStore()->getUnusedPropertiesSpecial(); though I assume that's related. By the way, it's strange that Special:Properties now lists unused properties as well, but that might be on purpose, so I don't know if it's a bug.
Probably this bug 18406 is somehow related to this too. I also think that unused properties with a datatype declaration should only be on Special:UnusedProperties.