Lion can't see pictures put into folder, then deletes them.

[Capex]

I am having a rather frustrating problem. I am doing a stop motion for a school project, but when i put the photos into a folder, i went to view them and they weren't there. Later on, some of them appeared, but if i went to either open or quick look them, they weren't there. It said "application not found" or when i quick looked them, there was only a like document icon. The files have disappeared. I have them on a flash drive at school thank goodness, but the copy i had on my computer is weird. Sorry for this.

Help!

Second: If I were to downgrade back to snow leopard, could I still use my @me.com email I acquired? What would be the biggest things I would lose downgrading?