Here's something that needs clarifications:
"If they do end up using ideas that you have pitched, and you are not under any contract with them, then you own the rights to the work, usually."

The usual disclaimer applies; I am Not a Lawyer. But AFAIK, you own rights to work that you have executed. If you are a photographer, then it's your photograph. However, nobody can copyright an idea. For example when the first spreadsheet program (VisiCalc?) came out, and later the first wordprocessor program, their ideas were a killer app in itself. Nobody had programs like that before, so arguably that was the idea. While their execution (the code) could not be copied, many others could write their word processing programs, and soon after Electric Pencil there was WordStar, Apple Write I, Samna III, Word, WordPerfect and Scripsit. The first one is not the most famous, nor most widely used - yet no lawsuits have been filed, because even if the other word processing programs have the same idea, their code is different so they are, different.

If your business is selling ideas as well as executing them right you shouldn't be showing ideas to anyone without having them sign a non-disclosure agreement. It is your livelyhood, and it can not be copyrighted.