The broom ride behind his uncle, the banter, and suddenness of the whole affair affected Al as any Weasley family event would have. But Mum seemed happy, laughing, as she draped her dress over Al's flat chest, rubbed rouge into his cheeks, and planted a bonnet on his head.
She grinned and acted pleased and youthful and dashing in Dad's jeans and jumper, and never once questioned Al's mental heath or his Severus-focused sexual preference. So Al did not voice his return complaints of being prodded and poked and touched. Clad in itchy and previously-unworn-by-him clothing, Al only hmphed, and grabbed the lipstick before Mum had a chance to put it on him herself.
"Please do something," he asked Scor miserably later, squinting through the eyelashes smudged thick with sooty clumps. He desperately wished for the knight of armor helmet to wear over his head, not this bonnet! At least he still had his sock suspenders and his wand, even though he didn't have a robe pocket to stick it into. Scor snorted and helped Al to transfigure his quills into a feather mask to go over his face.
It was only later that Al began to realise the gravity of the situation he was in: about to be late arriving home, away from Severus, in the middle of the Forbidden Forest, without means of individual transportation back besides walking. What time was it? Past nine, surely.
Not informing Severus of Current Event seemed like the most sensible thing to do. Jamie asked him to keep a secret and Al was never a particularly good liar but he didn't have to lie yet: he didn't need to say a word.
Thus, he did not speak of it.
There were other reasons not to mention this to Severus: this kind of Weasley affair would not have been, at all, to Severus' liking. And while it was Al's obligation to family to stand there as Mum fussed over his dress and his face, there was no sense in Severus enduring a similar discomfort. In fact, it was best if Severus omitted seeing the entire Weasley clan enduring mutual discomforts in the name of a family prank. There were many more graceful situations to observe, than this particular night.
And yet, Al couldn't help but want Severus here. He was lonely in a crowd. At the same time, he dreaded the moment - anytime now - of Severus' Patronus arriving to find him with an inevitable question.
The last thing Al wanted was to have to send his own back with a lie. Or a lie by omission.