I'm afraid that you are, in fact, incorrect.

"On accident…

A far less commonly used variant of by accident - on accident, is almost exclusively used in the United States - and incorrectly so. Even there, no one uses ‘on accident’ in writing; it's only a spoken English term. In fact, it is considered incorrect to be used at all.

Now, some people tend to use on accident as they rationalize that it must follow a similar structure to ‘on purpose’ although the meaning is completely the opposite. Yet another cause of confusion is interestingly the word 'accident' itself!"

- [link to www.grammar.com (secure)]

Note that rather than someone's opinion on writing, we quote.. <gasp>... grammar.com?

Yeah, I'm one of those. I can deal with bad grammar (barely) but it really grinds my gears when people DEFEND bad grammar.

Having said that, I hope you have a good day!