Ten days ago, we fixed a bug on a large application and the hot fix has created a disappearing of some data from the user point of view (side effect). Data are not deleted, but have been set to hidden status.

It could be possible to get the data back, but the thing seems to be hard: we've already spent 10 days to understand and reproduce the problem (mostly with SQL queries but sometimes it is necessary to update the database to test the application logic).

My questions are :

• is 10 days a normal amount of time for these kind of problems?
• should we keep on and retrieve the data or should we give up this work (so the customer-relationship person will tell these users sorry for the loss, but your data have disappeared or maybe tell nothing at all)?
• what can be the signs that shows that we should stop to search for how to solve this issue?

Edit about the context : we are a small team(3), users are not the customers, and lost data are not about the users money, bank or vital data. This is a question from a confused developer about development methodologies and business concerns, not about how we should deal with the customers.