If I understand correctly, OP took the original video (for which he hasn't shared the file name), and used the app inshot to remove the image, but not the sound. (Although I assume that the OP did not recognise the password as being their own).
From our point of view, OP, that really gives us very little information to go on. At the very least, the original file name and the full directory where you found it ought to be some indicator. If it is in your DCIM folder, then the phone recorded it, but if you found it within an app's directory then it may be something else. (E.g. part of a downloaded game or something like that).