I'm wondering if you have any memory that belongs to your oracle user still hanging around. I had a similar problem when I deleted everything in the Oracle FS without stopping Oracle! (we all learn from our mistakes!) If you cannot unmount the filesystem, I suspect this might be your problem.
Check to see if there are any processes running belonging to your Oracle user (ps -ef | grep <oracle user name>). If there are processes out there and Oracle isn't running, you may have deleted u02 without bringing down Oracle. You could probably kill those processes.
Then type this: ipcs | grep <your oracle user name>
If Oracle isn't running (which I would think it wouldn't be if you deleted the executables) you should get no output.
If Oracle isn't running and you do get output, you can use ipcrm to remove the memory stuff that is hanging around. See the man page for ipcs and ipcrm for more info.
If there are a lot of ipcs listings, sometimes it is just as easy to boot.
Good luck.