Corrupt redo log file - database only gets to mount

Ok. This isn't my system I'm writing about, but, since I'm tagged as the UNIX/Oracle expert (a scary thought on the Oracle side since I only started doing the DBA work at my plant 3 years ago as a small part of my overall responsibilities) by all of the plant IT people in my company, I got called to look into this today. Fortunately, not my problem to solve and I think they rather hosed themselves, but here's what the situation is. I'd appreciate some input as to if I'm totally off base on the solution.

Database is 8.0.X on HP-UX 10.20. They couldn't connect to the instance and bouncing it resulted in ORA-00333. Checking the alert log told me the redo log file for group 1 was getting an IO error at the OS level. This should be an easy fix, but the structure of where files were located is a mess and I found in short order that the redo logs were not duplexed (doh!). The database is in archivelog mode and they *think* they have a full system backup that contains the offending redo log file. We tried a few things, but nothing was successful either because they required the database to be open or because the offending log file was the active one.

Any obvious thing we're missing to get the database to overlook this bad redo log file?

If they do have a backup copy of the redo log, they should be able to drop it in place and recover from there, right?

If they don't have the backup, they're rebuilding, right?

Insights appreciated.

-- 
Jeff Traigle
traigle_at_si.umich.edu
http://www-personal.si.umich.edu/~traigle/