I have a bathroom renovation in progress. Originally, I had a shower, tub, and 2 sinks in the bathroom. The shower and tub are being combined into one large shower. The tub hot/cold lines were capped. The shower hot/cold have been roughed into a Delta Universal valve. One sink was left in place, and the other was moved over a bit.

The problem I am having is the contractors have finished the plumbing and moving onto tile preparations, but I have no hot water in the rest of the house. They are stating that it is a coincidence, and something must be wrong with my hot water heater, as they didn't do anything that could cause this behavior. The pilot light is on (I even turned up the temp setting and saw the burners kick on for a long time). The pipe coming out of the hot water heater is very hot, so I know at least at the source things look good. When I turn on hot water at any faucet, it is cold (and actually gets even colder when left on a minute).

What could be going on here? Is there a change in pressure or air or something else that could be in the line due to them capping one piece and moving another?