Actually, no, it is not a "whole different type of theft". It's simply theft by an employee rather than a customer. But theft is theft.
This line of thought does not help you Thieves employ a variety of schemes to steal. Some are more common than others. But what of it? You cannot logically argue that because what you did was less common than what other employee thieves do that it is not theft. Theft is the taking of the property of another without consent of the owner. If the way you took the property was the least common ever that would still be theft. So get away from the idea that just because what did does not match the most common theft schemes out there that a court will dismiss the case. You are grasping at straws with that sort of argument.
Theft is a general intent crime. That means the prosecution only needs to prove that you intended to take the property without paying for it. The problem for you is that this is easy to do because a person is presumed to intend to do what he or she actually does. For example, if you walk to the store, it's pretty much a sure thing you intended to walk to the store because you would not have done that if you didn't intend to do it. So if you grab a bag of chips without paying for it and eat the chips, the presumption is that you intended to take the chips, not pay for them, and eat them because that is what you actually did. It would be on you to provide some compelling evidence to a jury to disprove that you didn't intend to take them without paying for them. Hint: simply testifying saying "I intended to pay for them but just forgot" isn't very persuasive as pretty much everyone who steals from a store, whether customer or employee, will try to pull that line.
The prosecution can rely upon the presumption I just mentioned. You'll need to convince the jury otherwise. A judge is not going to dismiss the charges based on your intent argument. That is an issue for the jury.
Really, see a criminal defense attorney for help with this. You don't understand the law or court rules and you need someone to help you organize a viable defense (if there is one). If you proceed based on the sort of arguments you've made here you're going to have a hard time.
TV shows and movies give a very bad impression of when the Miranda warning is required because it makes for good drama to show the cops reading your rights the moment they arrest you. The way the law works is that the Miranda warning is required when both of the following conditions exist at the same time: (1) you are in custody (e.g. under arrest) and (2) the cops are going to question you. So if you are not in custody the cops can question you and need not give you the Miranda warning. Or if you are in custody but the cops don't question you then Miranda is not required either. It's only when both conditions exist at the same time. If the cops do question you while you are in custody and do not give your the Miranda warning prior to questioning then the remedy is that any statements you made during questioning may be suppressed by the court and not used against you at trial. IT DOES NOT REQUIRE THE COURT TO DISMISS THE CHARGES. So if the state has sufficient evidence to go ahead and prosecute you even without the statements you made that got suppressed the case goes forward and you can still be convicted. So if you made your statement after the arrest, the cops probably needed to give you that Miranda warning, but that only matters if the state wants to use your statement against you.