Location turned off on phone so you can't track them and you forgot their Apple password (or they changed it, but pretty sure just forgot).

Let's say that you are fairly certain they are up to no good but are numb to their current choices. And say you already suspected they snuck out 2-3 times this week and came back alive.

Just let it be until you are sure you can use it to your advantage or that you are more prepared to track them next time?

Go sleep in their bed (Perhaps even naked) for a fun surprise when he comes home?

Call the police abd report the care they took missing, Hope he gets arrested?

Just leave it completely be like your dad did when you snuck out and he clearly knew (even though that's a bit different because you had good grades and were just doing silly stuff with your friends, not actually bad things).