I don't understand the logic here. Why not report it after the date? A rather strange number of coincidences... having a "prior arrest record in another drug use case" and not reporting his phone being stolen, only to be arrested for a drug event again.
Nevertheless, I would never cheat on my spouse, so I would not be in such a situation to begin with.
Regardless, it is possible that we are not really hearing his side of the story properly. He doesn't even have a lawyer, which is extremely concerning. Regardless of whether or not he is guilty, he deserves the best defense possible.