It has been my experience, when I have had a problem like this. The vibration motor is close to the plug therefore it receives power. Somewhere beyond that is a break in the circuit I've never had experience with this phone that you're talking about but I've had experience with several phones and have done the same thing and it's always been a broken connection between the charging port and the battery. Unknowingly , because you have to spread the phone wide enough to get your fingers in or whatever instrument you're using to work with after you connect the wires, ribbon connector or however it is connected. I know that it is not uncommon for me to accidentally unplug the connector are pull a ribbon away from the connection. I have even done it to the extent where I could look back inside the phone and it would look like it was connect but it would be pulled out sometimes ever so slightly enough it wouldn't make a connection. Your battery connections probably going to be opposite where it plugs in if you can charge your battery in another device put it back in the phone you're having trouble with and see if any part of the phone comes on. If it does check your button near the charger port see if they work if they don't but you can turn the phone on with the top buttons and navigate with the screen you're broken circuit is going to be between your charging port and your battery contact affecting the the ability for the phone to make connection with the battery and the charging port. Please , keep in mind because I have no experience on the phone that you are working on I'm just telling you about similar experiences I've had working with other phone. Every single time it has been due to an unplugged connection, except for one case in a Samsung Galaxy s2 where I broke the board between the charging ports & the top of the phone when my screwdriver slipped went through the board & into my hand. I hope any part of this helps you.