Two families got the same envelope number

[John Dykema]

I have a situation where John Doe was assigned to #188.
In 2003 he transferred so I changed him to #8188 (that's the range we use for transfers)
Later in 2004 I assigned #188 to a new person, Bob Whoever.
Late in 2009 I reassigned Bob to 8188 because of non-use of envelopes (although on Thanksgiving Day he surprised us and gave).
Problem now is that two familes have the same 8188 number and John Doe got a statement for Bob Whoever's Thanksgiving day gift.
This one got away from me because I "know" that two families can't have the same number (family members, yes but not different familes).
Do I have this figured right? Is there a bug

[Tracy]

Some place along the line of changes something like this happened. We've not been able to pin it down 100% but most of places this happens has been corrected. Support will be able to assist if you have a really good approximate dates of when the transfers to the 8188 and the new 188 happened before being transferred.

[John Dykema]

The exact dates are as follows:
John Doe was changed to #8188 on 7/1/2003 due to non giving.
Bob Whoever assigned to 188 on 11/8/2003 (no contributions were on record at that time).
I changed Bob Whoever to #8188 on 10/10/2008 but it did not come up as a duplicate.