If you removed the test kit stick, or it fell out, at any point after you placed it in the test tube, the result of the test is not valid even if you immediately replaced the test kit stick. The test kit stick must remain in the test tube for at least 20 minutes as shown in the instructions.
Therefore, do not consider your result an accurate indication of your HIV status. You can dispose of the test kit, reorder a new test kit, and carefully follow the handling and testing instructions on how to properly use the kit.