Other mistake: Pilot episode Mr. Lucas is holding the mannequin together with Miss Brahms. Mr. Grainger walks by and is appalled by the state of undress of the figure and says "Well, it's hardly sufficient, is it?" You can see the camera getting randomly out of focus in a bad, noticeable way. (00:03:20)
Other mistake: When Mrs. Brahms is talking to Mr. Granger, Wendy Richards' voice cracks stifling laughter when she says "Mrs. Slocombe didn't like to take down your trousers without asking you first." (00:18:00)
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