Quick question ladies

Okay so I took an opk test earlier it was positive I got home from work and I had to pee and couldn’t wait to get one of the cups and I wanted to re test again and about a hour later after I was drinking lots of water because I just wanted to be sure I took another and the line was like non existent is this because the urine was to diluted of did my positive go away that fast going to retest in the morning