出没 implies something appearing unpredictably or lurking in an area. It's often used for dangerous animals, criminals, or supernatural beings. The pattern is 有...出没 (there are ... lurking/spotted).
mistakes
The 没 here is pronounced mò (4th tone, 'to submerge/disappear'), not méi (2nd tone, 'not have'). This is a different meaning of the character.