Is it possible to "swim" in a vacuum, taking advantage of relativity? (Is this a joke or hoax?) is a question I posted just now. Everything seems fine now, but while on this page which is an old question of mine: Why does moderately distant lightning sound the way it does: relatively quiet high pitched thunder first, and then much louder low pitched thunder? I clicked asked a question and and was presented with what looked like an edit page for this other old question of mine: Is it physically possible to have and how dense is styrofoam with helium or hydrogen replacing the air or whatever gas fills the spaces in it? . In haste I decided to use it anyway, changing everything except the tags. So when I posted the question the tags were wrong. I saw that and replaced the tags. So, as I said, everything seems to be fine now. But why did I get that editing page of a random other question of mine instead of a blank edit page?
I'm having a little trouble following you, but I think you're saying the following:
It occurred to you to ask question A, which didn't exist because you had just thought of it. You happened to be be looking at question B and hit "new question", but the new question page was populated with the text and tags from question C. You replaced all of the question C text with question A text, and now questions C and A both exist, which was your goal, but you are confused about the intermediate step.
One possibility is that this is a caching problem, either within your browser or within the SE software. When you're editing a question or an answer, you occasionally get a message under the edit box "draft saved"; sometimes you will close a page with a partially-written answer, navigate back to it later (perhaps many days later), and your draft is intact. (I think the way this works is that there's just one draft associated with your account on the site, so if you start working on an answer to a different question your other drafts will disappear.)
It sounds like, in your case, you were presented with a saved draft of your previous question in the "Ask a Question" page, which you replaced with your new question. (An edit would have shown up in question C's revision history, but there's nothing recent there.) The desired behavior would be that, having asked question C, its draft would have been deleted rather than presented to you again. But caching problems are tricky.