Hot water tank - no hot water

Hello. A plumber replaced some sort of pump to do with the hot water tank yesterday and now we have no hot water. The boiler, central heating and everything appears in working order so I think he forgot to, pardon the terminology, allow the water back into the tank. How do I do this? I can see 3 turning valves, 1 for hot water isolation, one for cold water isolation and another unmarked one.