This is how the Tracy brothers find Scott is missing and the search for Scott goes in Thunderbots Are Go!.
[Virgil walks into the dinning room at the Tracy household on Tracy Island]
Virgil Tracy: Hey! Anyone seen Scott?
Gordon Tracy: Sorry, Virg. Haven't seen him since yesterday.
Alan Tracy: Shush. Do you hear that?
[There is a snoring noise]
Virgil: Yep. Definately.
Gordon: Maybe Scott's still asleep.
Virgil: Let's check it out.
[They head into Scott's room]
Virgil: Yep. Still asleep alright.
Alan: Hey! Scott, time to get up!
[They approach the bed]
Gordon: Scott? Can you hear us?
Virgil: Scott! Get up, will ya?!
[They find MAX in the bed]
Virgil: [screams] MAX? What are you doing in there?
[MAX jumps out of the bed and hands him a note written by Scott]
Alan: It's a note from Scott!
Gordon: What does it say, Virgil?
Virgil: [reading the note] Dear, Alan, Gordon, Virgil and John, I have run away. Because, I don't aprecciate Optimus' attempt to improve our technology. I mean, he can't just turn it into his own. As long as you guys are okay with it, that's fine. But I'm not working with Thruster, no chance. So, I decided to quit International Rescue for my own safety. Please take care of Grandma and the others. Good luck with your new partners. Lots of love from your brother, Scott Tracy?
Alan: Scott ran away for no reason?!
Gordon: That just ain't cool.
Virgil: Come on. We've gotta tell Optimus.
[They head down into the Autobot Base]
Optimus: Virgil, Alan, Gordon. You look worried. What is wrong?
Alan: Scott ran away!
Rainbow Dash: He what?!
Thomas: Why would he do that?
Virgil: Because, he can't compete with our vehicles being turned into robots. We have to find him now.
[Suddenly, the alarm sounds]
Optimus: Ratchet, what is happening?
Ratchet: It's an SOS. From Scott.