Formal:
* Misplaced
* Mispositioned
* Malpositioned
* Improperly placed
* Erroneously positioned
Informal:
* Put in the wrong place
* In the wrong spot
* Out of place
* Off-kilter
The best synonym will depend on the specific context. For example, "misplaced" might be appropriate when describing a lost object, while "out of place" might be better for describing something that doesn't fit in with its surroundings.