Existence is reserved for things we have access to. Possible existence implies possible access. Actual existence implies actual access. Non-existence implies no possible access.

It is certainly possible to describe things outside of all possible access. For example as mentioned above we can talk about "non-actual or nonexistent things" and "possible worlds" that we can't access because they are counterfactual or because they are a separate reality. But when we talk about things beyond all possible access, we are just making up stories, and we can say anything. For example: All non-existent things are blue, and they are also simultaneously non-blue.

This reshapes the question to "Can something exist even if we don't have access to it.".

Although I am tempted to say that it certainly seems possible, I believe that the best approach is not to make any claims about anything beyond our access.