Hello, I am using latest version of your mod and is not working as advertised.
Replicate steps:
1) Build an underground belt without pair
2) Press the shortcut to find the orphan once
3) Observe the screen : no arrow shown
4) Check mod message:
Found 1 orphan
Orphan markers cleared

Notice that I pressed the shortcut only once. No matter how short/fast I press the key, both messages appear, indicating that the mod deleted the arrow immediately after showing it.

Edit: Turns out it was a shortcut conflict with Auto Trash mod. Once I changed the shortcut, it worked as expected. You may post a warning in the description page, as that mod is quite popular.