Meaning of "some higher order"?

Hello everyone. I am reading a novel, and I came across this expression. Could you please let me know its meaning?

On my way to the shower I spotted the mound of salt on the carpet still bearing the grooved imprints of Clara’s fingers. My God, she had been here less than twenty-four hours ago—here, in this very apartment, sitting on this very carpet, barefoot, with chocolate cookies wedged in between her toes. The idea seemed unreal, impossible to grasp, as if some higher order had suddenly descended to pay a visit to my arid, dull, sublunary landfill. Yesterday we were together, I kept repeating.

- André Aciman, Eight White Nights, Sixth Night

This is a novel published in the United States of America in 2010. This novel is narrated by the nameless male protagonist who meets Clara at a Christmas party in Manhattan. Now the protagonist is taking a shower, thinking back about his yesterday with Clara.

In this part, I wonder what the underlined expression means.

I am vaguely guessing that some high-level person was paying a visit to him, but I am not sure what that means...

Would that be a divine existence, perhaps, as opposed to his "sublunary (this world under the moon) landfill"...? (But I am just guessing. )

Thank you very much for your help.