[l33tman]

No you're understanding correctly (I think), the behaviour of a single detected particle depends on all possible paths it could take to get to the detection.

This is fundamental to 100 years of quantum mechanics and underlies most of physics including all semiconductors, materials science, chemistry, lasers, etc. The double slit experiment is just a very good illustration of the principle boiled down to its essentials, which is why it's everywhere in pop-sci. It makes for more accessible story than describing how a hydrogen atom works.