A helpful tip I found in the recesses of google earlier.
My iphone recently had an...accident...and the vibrate was just dead. Hard resets, powers off, switching vibrate on and of....nothing would make it come back.
Except one thing....Pick up the phone, give it a shake. Job done, vibration back.
Didn't shake it any harder than say, a medicine bottle pre-consumption.
Hopefully of use to some folks out there