This whole “intended to be there/or not” argument is bizarre, and is too difficult to prove one way or the other. Unless someone is Eliza Thornberry and can talk to animals, there’s no way to know with certainty.
In the case of escaped/released pets, we have no way of differentiating whether something was deliberately released, or an accidental escapee. The only fallback would be to look at whether or not the species is native, not the individual specimen. Throw “intent”, and humans/organisms that are there because of human activities out of the equation, and a lot of these would become much more clear cut.