Sorry for the late reply

I did what you said, but impossible to recover the record.

The record is not visible even with a full scan and after have drop the index

I used the tool IBSurgeon and nothing, the record seems definitively lost.

My database is on Force Write Off, may the cause of the problem ...

This week I had exactly the same problem on an other database !

The same record was lost.

In my application one field of this record is frequently updated (on each operation in fact), 

Without it my application can't start, so I think to move this field in an other table, but I think the problem will not be solved with this ... just moved (I will set Force Write On too)

Thank you for your help

Eric