How to find which room a hue globe is assigned to by serial number?

I have a globe which has previously been used. Likely was not removed in the app, just physically taken out and replaced with another (I don't remember). Now I can't re-assign it as search fails ... both auto and by serial. I'm wondering if this is because it is already assigned. So I need to find it in the app, delete it and hopefully can then add it back in. But the app doesn't specify serial numbers of each globe. The globe works when it is installed and manually switched.