What it's happen with IDs from MediaStore when some items are deleted?

Question

Hi!

Let's suppose that: I delete an item from my sdcard and after I unmount the memory card! What is happen when Android rescan my sdcard for changes? In MediaStore every row have an _ID so after I delete an item what is happen with this _ID: it remain in MediaStore, it is associate with an other item or it is removed permanently?

Thank you!