Lucifer knows how this is going to turn out:
He is going to push Sam into the closest dressing room to whatever blushing sales associate he has gotten finished chatting with. Lucifer will then casually mention the butt plug Sam put in this morning while he is attempting to change into something that doesn't deserve the grace of his eyes, let alone his skin. Sam will be a girl about it and blush; he will have forgotten that no one can surprise the devil. Especially when they have evil intentions.
He will then kiss Sam, long and slow. Using the kind of romance he knows Sam likes to delude himself into thinking he has. Once Lucifer feels like he's done enough playing Prince Charming, he'll start doing little distracting things like biting Sam's neck and shoulders, just because he loves how unsuccessful Sam is at using his inside voice.
He will be rubbing Sam's torso under his shirt simultaneously, and murmuring filthy things in Sam's ear in between kisses. Making Sam turn red is as important as making him come. After teasing Sam's nipples for so long that anybody who didn't knew what they were doing would have a guess then, Lucifer will deem it time to get to the good part.
Since Lucifer will have already undone all of Sam's hard work getting dressed, all he will have to do is place Sam's hand on the low bench attached to the wall and firmly shove his face into whatever clothes he snatched off of the rack before then. Sam will be whimpering by that point anyway, since Lucifer has turned him into the impatient type. Lucifer will consider being gentle and caressing, but will decide against it because Sam knows what he signed up for.
It will be his favorite butt plug, the metal one with a textured teardrop on the end of a rod thin enough for him to get tight with it in. Lucifer will congratulate Sam on his kinkiness, and then reward him.
