Only someone with intent to plagiarize will use a checker. But the chance of you writing with the same word by word in a sentence is totally impossible.
The chances of writing the same words is impossible, but the chances of writing the same idea in similar ways is very possible. If the later happens, it may look like paraphrasing.
Moreso, I pointed out that people overtime tends to confuse their original words and/or ideas from adopted ones. This happens to especially great readers, in order to be very sure, it wouldn't cost much to run a plagiarism test before publishing.