* Missing article: "Toy" should be preceded by "a" or "the" depending on the context. For example, "It was their toy" or "It was the toy."
* Incorrect pronoun: "There" is an adverb, not a possessive pronoun. The correct pronoun is "their."
* Missing subject: The sentence needs a subject to tell us who or what "it" refers to.
Here are some corrected versions:
* "It was their toy." (Assuming the "it" refers to an object that belongs to someone else.)
* "The toy was there." (If the sentence is about the location of the toy.)
* "They left their toy there." (This provides more context about who left the toy and where.)