what is the word for something which may exist or may not

Solution 1:

You may purport that your object exists.

pur·port·ed adjective -ˈpȯr-təd\ : said to be true or real but not definitely true or real

"The purported one eyed unicorn is said to be found only in the gangha swamps of Tashkent."

Beware though, the verb form carries a strong negative connotation.

purport 1: to have the often specious appearance of being, intending, or claiming (something implied or inferred) ; also : claim 2: intend, purpose

You might be better off using allege/alleging/alleged:

1: asserted to be true or to exist 2: questionably true or of a specified kind : supposed, so-called

Solution 2:

I believe the object under discussion is putative (from the Latin for 'thought' but without the connotations of 'assumed').

Solution 3:

A hypothesis in science may be completely baseless and incorrect. If it is so, studies will not support it's existence. It doesn't mean it wasn't a hypothesis. Another definition of hypothesis is something taken to be true for the purpose of argument or investigation; an assumption.

Let's use an example of the Loch Ness monster. Nessie is referred to as:

reputed, supposed, anecdotal, speculative, mythical, and alleged.

One of these adjectives, especially speculative, may fit your needs, as you are, from my understanding, speculating on the existence of something.

Other words for your consideration are postulated, proposed, presumed, assumed, potential, or hypothetical.