glIsTexture with Cubemaps

Normally you can determine if a texture has been glTexImage’d by using glIsTexture, but is there any way to do that for a cubemap where most faces have been uploaded but not all, and you would like to determine which sides have been uploaded?

Call GetTexLevelParameter on the 6 faces to query the sizes (which would default to zero)?

IsTexture doesn’t tell you whether there’s been anything loaded – it will return TRUE as soon as a numbered texture object has been bound, even if you’ve never called TexImage.