Table is dropped but ibd file still exists
You can go to the OS and drop the file because the data dictionary in the system tablespace (ibdata1) does not know of the .ibd file's existence any more.
I wrote a post 2 months ago about deleting temporary .ibd files : temp table (#sql-7a87_230c32.ibd along with its .frm) still exists on slave. It applies in your case as well.
Give it a Try !!!