Recover Deleted Voice Memo
Once it's deleted, it's gone.  You can check your last iCloud backup.  If it was after the recording but before the delete, you might be able to get it back.

There's about a dozen iPhone recovery-type tools on the net.  A little searching will identify who they are and how to get them (I won't list them here because I don't have experience with them).  They claim to be able to recover voice memo's but YMMV.