Oh man that sounds so fucking great to me as an experienced powder rider....
Don`t feel bad though as what you experienced (frustration) is something we all went through on our learning curve riding in the deep off piste powder. Trust me though, as you start to get a feel for riding in it you will learn to shun and hate the grooming cat.....
The best way I have found to start learning to ride untracked powder is to dive in and out of it from your favorite groomed run and make sure that you do this on a steeper run. The green or easy blue run is NOT your friend on a deep powder day. When you eat shit in the deep, you want it to be on a steep enough hill that it is easy to get back up again and get moving.
Powder riding is like taking everything you learned about good snowboarding technique on groomers and throwing it out the window. With powder, you don`t want to employ the leaning forward and and using the front foot to initiate your turns (later on, you can go back to riding centered but for now think about shifting your weight aft).
The best approach to begin to get a feel for control in the powder is to move back and use the rear foot a lot more to push and pull the tail of the board to gently make direction cahnges. Typically, an inexperienced powder rider always tends to edge too much which causes the board to abruptly dive down deep and throw you.
Additionally, your turns at first need to be more open ended S turns where you keep the nose of the board pointed more down the fall line. Turn completion in deep powder for the innexperienced rider is going to dump you.
I think the best analogy I can use here is to imagine your board as a jet boat on a lake. First off, you have to achieve and maintain enough speed to get up on plane like a boat has to do. Like a boat, the steering comes from the aft by turning the motor so your rear foot will in fact act a lot more like a rudder, but go easy with it at first as it is easy to oversteer. Maintain low edge angles and do everything gently just as you would in a boat.
Ano0ther thing that helps maintain float is something I call "porpoising" like a Dolphin. This is a gentle up unweighting where you keep popping the the nose up out of the deep by pulling it with the front leg. A gentle hopping up and down also helps keep you up on top.
Now, once you get the hang of the basics by riding like this, you can then reintroduce more correct riding techniques such as staying centered and only shifting your weight aft and forward as needed and using both feet to gently tilt the board as needed. For now though, these techniques can help you get back out in the deep shit and progress without quite so much frustration.
When you do feel frustrated, understand that it is normal and while we all crave powder, it has a definite learning curve like everything.