Can't say that I have.
Maybe it was detected in saliva but not urine of you were well hydrated? The more hydrated you are, the more diluted the ketones become.

Fun side note: as a child (so early 90s) my Dr would have my mom dip one in a soda if we were at a restaurant to check it was diet (i was skinny kid and had a number of wait staff slip me regular thinking I had crazy mother). I was always mortified, but it works