I had frozen pipes: a hot water pipe in a bathroom and both hot/cold to my washer. I'm new to this house. I finally got them thawed with no burst pipes. I had turned the water off and drained the water to do this. When I turned the water back on, all was great - at first. Now I have cold water coming from the hot water heater. I checked it and the pilot is lit and heating. What did I do?? What CAN I do? Thanks a lot in advance for the help.

I finally got them thawed
How do you know that? Do you know where and all the places the hot water lines were frozen.

If the main hot water line out of the water heater is frozen and you open both the hot and cold one faucet and the hot of another faucet. Cold water will come out the spout of the first faucet. Cold water will also go out of that faucet, through the hot water line and come out the hot side of the second faucet. Suspect you still have a frozen hot water line between the water heater and the first faucet.

Close the cold side of all faucets, open the hot of all faucets (turn single lever faucets to hot side). Do you have any water coming out of any faucets? If not then hot is still frozen.