Hey pikachuH -
For the Health_Pickup_Small.uasset, I am not certain as to what type of asset that it is, but with a file size of 2kB it looks like it is a redirector in the project files and not the actual asset. It could also be an issue of version. Did you recently move that asset or project from one engine version to another? If so, try to go back to the old version number and see if the asset reappears in the editor. Then try to migrate instead of copying in Windows Explorer.
Thank You
Eric Ketchum
