Can you please clear your cache and data from your browser. If you already did, open your file manager and look on thumbnails or on download or from each folder (if not sure where it was saved). Once found, tap on on the 3 dots on the lowest end of your screen then tap on the select file or folder. You have the selection to delete, cut, or copy. In your case you may have it deleted. Please get back to me if still unsolved. Thank you.