Wow I've never heard that one before.
I saw a guy on Maury Povich who was deathly afraid of peaches, and a woman who was scares of cotton balls.
As far as I know I don't have any weird phobias. I freak out when someone I don't know walks behind me at night, but I think that's fairly normal...
It's more likely to break in a backpack than in a wallet.
Depending on what's in the wallet/backpack, it should be fine in either.
(unless you're planning on keeping some sewing needles, knives or broken glass in your bag or wallet)