Yes and no.
TLDR; They would be able to work out that you did something from the context. They might not realise what you did - it depends on how well they know psionics (Arcana check).
Reasons why they would know it is you:
You have to speak to them telepathically to use the feature, and telepathic communication is done in your voice. It is at least obvious that you are the one telling them the lie, per an unofficial ruling by rules designer Jeremy Crawford:
You sound like yourself when speaking via telepathy, although as DM, I allow attempts at telepathic deception. #DnD
Reasons why they wouldn't know it is you:
On a failed save, there is no effect.
The mystic's Occluded Mind psionic effect says that:
On a successful save, the target is unaffected. [...]
RAW, nothing happens. There is no effect to determine. However, if you tell them to believe something (e.g. "The sky is green"), they know that you told them, and they will at least think it is odd that you say that (e.g. "What? It's clearly blue!").
After the 5 minutes is up, and they see something to counteract your statement (the sky clearly not being green), they will realise that they believed that it was for a time, and remember you telling them that it was.
Perhaps your DM will rule that they saw the sky as being green for those 5 minutes, and remember it as such, though in any case, you are clearly the one who initiated....something: even if it was just an illusion of the sky being green.