One Inbox in Mail doesn't have a symbol beside it.

I find it strange that my one of my work inboxes doesn't have the blue mailbox symbol beside it? As someone with OCD, it drives me insane. If I rearrange the mailbox, it comes up...until you click on it and then it vanishes. My other 3 always stay there, but it never does. Include a picture where it is missing (green circle) and where it is on another work email I manage (blue circle). Please help me from going nuts!