I may be splitting hairs here, but I feel as though the difference between those two drugs is significant (In so far as how it relates to this case). Yes, you could at the very base level say both are speed, but there are differences and I will try to explain them while tying them into the relevance of BL's case.
Adderall is generally a short(ish) acting stimulant. Generally delivering a good 4-6 hours worth of speed-esque feelings. Vyvanse is a much longer acting drug. That will generally last 12 hours, sometimes more. I with no pride and true disgust at myself can say I have experienced times where I took Vyvanse at 7 AM and at 1 AM that evening still was feeling the effects and was not able to sleep. That's a very long time to be under the influence of drugs.
This raises a few questions for me. If he had been taking these for a few days, and not sleeping, the psychosis probably would have been very tough to deal with, especially if this is something he wasn't generally experienced in. Same goes for depression. I can speak to the crippling depression and thoughts that come post-stimulant usage. I am not even referring to abusing them and staying up for days. I have taken one vyvanse early In the morning to complete a 30 page research paper, and even coming down from that was a challenge.
These drugs suck you into whatever task you are performing while time is moving a lot faster than you think. I can easily see him pulling his car over, and getting sucked into internet on his phone and burning off 12 hours at the same spot. Also, if he was trying to come down before getting home to his insanely overprotective mom, I could see him sitting there that long. The thing is though, the cops who checked on him would not have said he was sober. His pupils would be a flashing/screaming red flag that he was under the influence of amphetamines. He'd be nonstop talking and chatty, so the police, Christian, and the people talking to him on the phone would have definitely noticed something, even more so if this was their first time interacting with him under the influence of this.