The Father Christmas Affair - S4-E7
Visible crew/equipment: When Mr Humprhries is talking about the whereabouts of Mr Grainger, explaining about the inability to remove the Al Jolson make up, you can see John Inman looking up before having his face shadowed by a boom mike.
Answer: It usually just means seeing something weird or unusual, perhaps something someone wouldn't believe you saw without proof. The phrase is usually "haven't got your gun", although some people replace "gun" with "camera." Basically think about a hunter spending all week in the woods looking for the biggest [fill in the blank] and the one day he goes out into the woods without his gun and then finally sees it.
Bishop73