All the time. I've always found it, but when it got overused and always fell out I just ordered 5 black ones for $2. You can definitely tell that it's a cheap one, but it works perfectly fine and you can't tell a difference while playing.
I usually just order more stylus' from the Nintendo website. It comes within a week. Since I don't play my DS much, I can wait for new ones to come in. Or I see if I can buy any from the local game shops
I just use my fingers and not play any games that basically require you to have a stylist like Yo-kai Watch, Pokemon Art Academy, and Happy Home Designer.
i have a few spare ones, so i use one of those if i lose one. and if i lose them all... well, i just get them out from the side of my bed because 99% of the time i lose them because they fell down there lol
but if none of them were there, then i'd probably use my finger, or try finding something among my sisters' toys that i could use as one.