There wasn't really a "Flash" phone, per se- though there were a lot of times when Bart thought it would a great idea. Then people could call the Flash and be all "Excuse me, Mr. The Flash? We're having problems with X at Y involving Z." And then zipzoom! They'd be there and they'd be all, "Halt, vile interloper!"
Okay-- he'd been reading too many comic books today when he was supposed to be "practicing" for an upcoming track meet.
The point was- no one that needed The Flash had a way to get a hold of him; so when Bart heard on the police scanner that the boy being held as a person of interest in the explosion of Midtown High School had admitted to being a mutant and claimed to have super speed-- well that sounded like a job for the Flash!
Or Kid Flash at the very least-- hey he couldn't help it that the Flash was currently unavailable (Grampa had to work late at the lab tonight).
So Kid Flash kissed his Grandma/Aunt/Graunt Iris and grabbed a snack and zipzapzoomed his way over to NYPD HQ. He didn't bother stopping to check in at the front desk (hey, the Keystone and Central City Police didn't mind him and the Flash stopping by) and only stopped when he found the only person to match the description of "teenage". He cocked his head to one side, standing outside of the holding cell to read Tommy's wrap sheet.
Sticking his hand in through the bars, Bart offered Tommy chips out of the bag he'd brought with him while he read, which only took about two seconds.
"Hi." He started, tossing back a handful of the chips himself. "The police said you have super speed. Did you blow up Midtown High?" He asked, getting straight to the point.