After digging around a little more in a source build of the engine I noticed that in AActor::DispatchPhysicsCollisionHit…
On the first collision ‘this’ AActor refers to the Sticky Gadgets which is expected. However after detachment, on the second collision ‘this’ AActor refers to the Sticky Gadgets parent, not the Sticky Gadget, which is why its OnComponentHit is never called.
I still have no idea why when the StickyGadget is getting hit it would be saying its hitting its parent though.