Everything Under the Moon

So today I was sitting in class and all of a sudden I got a really weird feeling from behind my back.
I first thought a student was sitting there so I ignored it.
And then I got a very strong smell of frankincense. I wondered who would pick a perfume like that so I turned around.
There was no one sitting, just a empty table.
And I still had the feeling of being watched.

Then the feeling was gone and so was the smell.

I never experienced that before at my university. I wasn't scared or so, Im Just wondering what that could have been and if it means something.

Was it maybe an supernatural entity?
And does the scent say something specific? I mean are there meaning to different scents like frankincense, rose etc?

It could just be someone Out-of-body (OOB) projecting during their private meditation in which they used frankincense for purification and protection. They might have intended to be in that spot or not, and you just picked up on it. No supernatural entity, just common garden variety psychism.

Do any of your friends practice the Craft that they might have been just saying "hi" as a tease? I had a college room mate that loved to joke like that. Hymph! she was a practicing witch at the time and I wasn't.

As far as I know there is no-one practising from my friends. Maybe it was just another student who wanted to wander the university when not physically present.