Working with hints/clues - Show vs Tell vs Nothing -ish

This is about the hints that the readers should notice as the story progresses - and should definitely notice upon re-read.

First off, I looked around for a bit and didn't see any questions on this kind of issue, but please correct me if you know of one.

I'm debating whether or not something fits the 'style' of writing that I'm working with, and if this is something that the reader would find odd or notice at all.

Just to set the stage:

I'm writing a science-fiction story, but science is more a 'behind the scenes' kindoff element than one which the story revolves around directly - at least to begin with.

The story is told from the third person perspective of my three main characters. The narrator doesn't tell us anything that isn't happening via the characters.

A major part of my story is the thousands of smaller and bigger hints that are spread across every scene, arc and so on. These differ for each character and increase and decrease in intensity for lack of better word.

These hints are there to slowly give the reader an idea that "things are not as they seem" or "there's more to this" and so on.

They are crucial, as the story takes place in "our world" - but through the hints alone (almost) we learn the hidden truth.

A majority of the story is about the mysteries in the lives of my 3 main characters.

I write their thoughts, memories, fealings, actions and so on.

The debate:

For the majority of my writing, it has felt natural what to write and what not to.

At a certain point I found myself having written; "When she arrived at school, she had forgotten all about it." [Translation, out of context - about a certain hint that's reoccuring]

When reading the paragraph, it doesn't stand out incredibly. However, I'm 100+ pages into writing and this is the only place where I've told the reader something that a character is NOT doing, actively or not.

This is not a thought or something that the character is actually doing. It is the narrator telling the reader something that the character is unaware of having done - which I haven't done so far.

This is telling, I know. I'm well aware that I probably wanted to put emphasis on the hint, making the reader once again 'think of the hint', but I'm unsure if this fits the style - or if it's perhaps frowned upon. It's efficient - as telling usually is.

So, the question(s) is/are probably something along the lines of:

Is this something that a writer should avoid when wanting to let the reader notice the hints by themselves?"

Am I obsessing about nothing, or should this not be written directly, if I want the reader to feel as if they are by themselves figuring out that something is wrong/odd/off/different?

I should note that the target audience is teens + adults, but not children - Perhaps a certain style fits certain ages better?