Running a magnet (even a super strong one) over the drive is no guarrantee that the data is unrecoverable. You have no way of knowing if the data was wiped or just a few bits of the allocation table got corrupted. Professional data recovery can sometimes get data from a drive that has been written over several times.
If it is "critical corporate data" as you say, you just eat the cost and throw the bad drive in the incinerator. Why risk $millions in lawsuits, intellectual property loss, and bad press for stupidity over a $200 hard drive.