Possible? YES, Easy? Not always.
First things first: DO NOT take any more dictations with the recorder that you want to recover files from in case you may quite possibly ruin your chances of voice memo file recovery.
Then connect your recorder to a PC with a recovery program installed.
Photo Recovery Software (also
recover Voice memos, audio and video files) is right what you need to use if you are running Windows. If you are Mac OS X users, turn to
Data Recovery for Mac.
But you should remember - the more you use your recorder, the less likely you may be able to recover the deleted files back! So STOP using the device ASAP. Hope my answer is helpful to you. Best regards!