I use this frequently with stuff like mdn, where I know the exact page and which search terms will get me there, but it's not worth bookmarking (I have Firefox set to only autocomplete bookmarks, not history). For example, "justify-content mdn !"
I've always been frustrated that the !mdn bang didn't have this behaviour by default. Looks like I can achieve the same result as you suggest with "! mdn justify-content" which should ease the change in muscle memory. Thank you!