After experience 'hinge failure' on a number of French's mustard bottles, I've come to the conclusion that whoever designed that little piece that keep the cap on was likely overpaid.
After only about eight uses, the little cap that is attached with two bits of plastic seems to invariably break and fall off! And, when it does, that little piece of yellow plastic really can fly off and can be hard to relocate. I can only wonder how many users are currently experiencing the same type of 'failure' considering the millions of pounds we consume every year!
I've written French's about this problem and will share if they respond.