Negative tests turning positive after a few hours

Da
My friend took a pregnancy test on Friday morning, it was negative.  She stuck it in a drawer then looked at it again about 10 hours later and it was positive.  Has anyone dealt with this before?  Do you think it's truly a positive?  I know you are not supposed to look at it after 10 minutes for accurate results but I would like to see what others have experienced.  My friend and her husband have been trying to conceive for over a year, she has PCOS and has not gotten a positive result ever.