My 14-year-old keeps sneaking his phone after bedtime, and screen time limits aren’t cutting it. Is there a way to remotely lock it during set hours without needing to physically grab his phone?
Yeah totally doable without touching his phone - if it’s Android, Google Family Link is your best bet, it’s free and you can set “bedtime” schedules that straight up lock the device at whatever time you want right from your phone. 
If you already set up Family Link when he got the phone you’re golden, if not you’ll need it installed on his device once (yeah, physical access required that one time), then you’re hands-free after that.
Honestly the nuclear option is just pulling the WiFi router on a schedule too - like $30 router app or just the parental controls most modern routers already have built in, kills the whole house internet at 10pm and suddenly that phone’s a lot less interesting. 