Just to clarify: After Lucifer spanks him a bit more, Luci just... leaves LMAO. And Adam is left alone hard and confused.
The second part takes place a couple weeks later, they started jacking off together at some other point, but they had this kind of weird unspoken agreement to NEVER say a word, during it, or after it, NOTHING, there was NO DISCUSSION...... until Lucifer decided to open his mouth and Adam PANICKED.