On an Android device images are stored in the phone's internal storage WhatsApp/Media/folder. If you have an SD card look for the same folder there. Using something like MyPhoneExplorer should let you do a search for the specific file... if it's still there
https://www.fjsoft.at/en/If using WhatsApp Web on PC then files are in your browser cache. Open Windows Explorer>>>Options>>>View tab>>>tick Show hidden files, folders and drives. OK your way out. Now follow this.... In Explorer click on C:/ drive>>>Users>>>the user name>>>AppData>>>Local. You now see a list of folders. Look for your browser - Chrome, Opera, whatever and click. Find Cache and double click. This folder has to be open. You now have thousands of files - all unknown.
To get round this download this:
https://www.nirsoft.net/utils/chrome_cache_view.htmlUnzip it and click on the ChromeCacheview.exe. In the app go to File and choose Select Cache Folder. In the pop-up copy and paste the url from Explorer address bar. It will be something like: C:\Users\Ally'sfriend\AppData\Local\Google\Chrome\UserData\Default\Cache. Forget the This PC part.
See the image on the download page. Your file, if it still exists, will be somewhere in the list. good luck.