Right after the Doctor saves Romana from the cliff they both go back to the TARDIS so Romana can change clothes and get shoes that are more suitable for the terrain. The follow conversation ensues.
Romana: Yes thanks.
Doctor: Still got the tracer?
Romana: Of course.
Doctor: Good. I wanted to check the stone circle again. [When they first got there the tracer led them to the stone circle as to the location of the third segment. Upon arriving there however the signal just disappeared.]
Romana: Well what do you think I was doing before you pushed me over the…? All Right. There was no trace. I promise you.
Doctor: Well its got to be somewhere.
Romana: Well it can’t be there.
Doctor: Well of course it can. [Pause] How’s your interspatial geometry?
Romana: Well, pretty rusty but…
Doctor: Good. Come on, let’s go then. [The Doctor leaves the TARDIS]
Romana: [Talking to K-9] Do you understand, K-9? I mean how can a thing be in one place and yet not be in that place?
[K-9 is pondering the question. You hear a lot of beeping and whirring as he can’t answer the question]
Romana: [Romana clears her throat] If you mean you don’t know, why don’t you just say so.
It is later discovered that the third segment is in the stone circle just in another type of dimension – HYPERSPACE.
Is this the reason why the island can’t be located by conventional means? Did they borrow this concept expand upon it and thus the reason for the mystery that is the island?