Positive then negative!

Hi ladies. So I took a home pregnancy the first test early result,the flat tip brand. And within a minute,I saw a pink faint line on it. It lasted for about 20 minutes,then when I took another look at it after about 20 minutes, it was no longer there! So my question is,was it a negative test from the beginning, or was it a positive??? I've never seen anything like that before!