Whatever user types in as the details (title, URL, steps) on a bug submission form should be stored till the bug is submitted (or the session is over) for preventing loss of work upon accidentally opening a new URL on the form page/refreshing the page and so on.
Still on this matter, changing the bug type shouldn't automatically swipe the typed-in data, specially because the steps are entered in separate fields and cannot be copied to the clipboard altogether.
If, upon changing the bug type, swiping the whole data still seems like a good idea, then I'd suggest that it's stored and gets back on the screen the case user changes the bug type back to the type previously selected.