I have accumulated 6 snippets but, when I go to the memoirs screen to place them, they do not show..

Click on the bottom right hand corner of your screen where your snip it pack would normally be. This will open up the screen to the snippet pack, the packs that you can buy, and the deja vu shop. Click on the first snippet pack it should have the number of Snippets you have listed on the pack

Sounds like a glitch. Hopefully restarting the game fixes it. If not, contact customer support by tapping on the green "help" button in the game settings.