SEP Field n. - Somebody Else's Problem field.

An SEP Field is used to hide something in plain sight. This phenomenon works on the principle that the human brain will filter out impossible objects and situations so as to preserve the sanity of the owner of the brain. When an impossible object or situation is encountered the brain decides that it is somebody else's problem and promptly deletes it from its perception of reality.

See Hitchhiker's Guide to the Galaxy.