This wouldn't work with either iOS or Google.I'm sure its a very stressful time. OP, do you have access to the OS account the phone uses, you don't need the handset. You can check location history via any web browser if location services were switched on.
Signing into an Apple account requires you to jump through hoops involving the phone. Google will spot the sign in from a new device and either send a text to the number with a one time passcode or pop an alert up on the phone itself and ask for confirmation. Either way it alerts the person with the phone that there's an attempt to access their account. It will also cross SIMs as well so even if the person has changed SIM, they'll get the alert on the new number.
There's also a legal aspect to what you're suggesting. Accessing someone's e-mail account without permission can fall under misuse of computers, and as it's a criminal offence you can end up with a criminal record. It's OK to say the police will probably turn a blind eye, but sometimes they either can't or won't. Yes it sucks, but legally there is no mitigation for it, and all it takes is for a jobsworth to be an idiot.