Yep, its really just a silly memorization phrase. Sin = Opposite/Hypotenuse , Cos = Adjacent/Hypotenuse, Tan = Adjacent/Hypotenuse.
Last year, I found out some students were using "Some Old Hippie Caught Another Hippie Tripping On Acid". I laughed at that one, but didn't endorse it for obvious reasons.
But as you said... one should not really need any trick and just learn.