If it's important it’s possible to use a third-party Mac app such as iExplorer to recover the original recording and AirDrop it back into the Voice Memos app on your iPad. First make a current full backup of your iPad on your Mac.
To test I create a 01:04 long recording in Voice Memos. I then trim it to 00:30 and save it. The user perspective from Voice Memos is that the original recording no longer exists.

Quit all apps on iPad. Connect iPad by cable to your Mac. In iExplorer on Mac navigate to where the original recording exists on iPad. It will be in the /Media/Recordings folder. Locate it by date and approximate time; it will have a .m4a extension. Quick Look the file to listen that it is the right one and confirm its length. Don’t manipulate any files or folders, just Air Drop a copy of the selected file to iPad from the Share menu. Quit iExplorer.

On iPad select Voice Memos to open it. If the trimmed video still has the same name, the system will add a digit to the filename of the recovered file.

If you go this route, don't make a habit of it. A better approach is to duplicate the recording from the Share menu, then edit the copy and leave the original untouched.