Did you check your hot water faucet leading from the hot water heater? Often they will forget to turn them back on. Mine did.

Your plumber's a dope.....and he knows it. With the application of a little integrity and an extra couple of minutes from him, you wouldn't have had to post. I would refuse to pay him until he comes back and finishes the damned job. This is just silly.

Is the cold side hot? If so, something is backwards. Could a valve somewhere be closed? Have you checked other faucets for hot water? Not sure what other questions to ask.

Bill

Hot water works everywhere else in the house. The cold side is definitely colder but the hot side doesn't even get to luke warm.
Our plumber is a friend who freelances...his real job is head of plumbing at a major hospital and does this for pocket money. he is coming back but I was just curious if there was an easy fix I could do.

Your plumber-friend will be able to diagnose and fix this. Understand it's confusing for you but it will not be for someone with knowledge and experience -- which he should have, if he's the professional you described. For whatever reason, he simply didn't spend enough time in the beginning to verify the function of what he'd done. There are only a few things it can be. I have little doubt he'll check them off and have you right this time.

What model faucet and does it have an anti-scald feature?