Are you talking about specific memories, or your ability of retention?
I hypothesize specific memories could be found through meditation and hypnotherapy.
I find I've increased my memory after opening my third eye (I found it has drastically improved my imagination and ability to visualize in my mind's eye, thus improving memory). Furthermore, I've found that positive affirmations can help memory, such as; "I remember everything I wish to remember","I have a great memory", etc.
All in all, meditation will help for both cases.