How can I un-trim a trimmed voice memo?
Today I used the free software iBrowse on my Mac (PC version also available) to view my iPhone 5 file sytem. I opened the Recordings folder and found all my Voice Memos.

The interesting part is, a Voice Memo I had Trimmed and sent to someone via iMessage, was there in both its original filename and full size, as well as another copy with .trimmed appended to its filename, evidently this is the shortened version I sent my friend. 

So if you use iBrowse to view your Recordings, there's a good chance you'll find your original Voice Memo inside there.

PS: I am using iOS 6.1.4 on my iPhone 5.