Steps to reproduce

1. Build the layout shown below.

   hopper	redstone dust
   redstone dust	solid block B
   solid block A

2. Power the dust on top of solid block B, for example with a redstone torch to the right of it or with a lever on solid block B.
3. Drop an item on the hopper.
4. Power solid block A, for example with a redstone torch below it or a lever on it.
5. Break the power source placed/activated in step 2.

Expected result

The item stays on top of the hopper because the redstone dust on top of solid block B remains powered and pointed into the hopper.

Observed result

The hopper collects the item. It is no longer locked by the powered redstone dust that points into it.