Received a urgent email from a business client saying that the application we support is completely broken. Their staff said they used the app to send several submissions that day but they did not come through. This is a major issue as these submissions need to occur daily.

I understand that this is a priority so I immediately check everything. I test the app, the server, check the database. Everything seems fine, but there's no record of these submissions. Maybe it's the specific device that was used. I reply saying that everything seems to be in order. Can I please be provided with more information about what occurred? What time were the submissions sent?

Client replies saying that the submissions were definitely sent and that the staff swear by it.

I now know something is up, so I remote into the the devices in question and check the logs. The app was not even used that day! I've got them! Those liars!

I am now quite pissed off, but remain professional and reply saying that we log all app events and that the logs show that the app had not been used at all that day. Now they have to own up to their lie. Right?

Wrong. Client replies with: The issue has been fixed. Thanks.

Can you believe the bloody nerve? The client doesn't even have the decency to apologise but rather insinuates that it was all our fault.

Well I'm not having that. I reply: It is great that the app is functioning correctly. However, I believe it is important to understand the cause of the issue as to prevent it from occuring again.

Client: No reply.

Well, if you want to waste other people's time, here's the fat bill.

Moral of the story. Don't trust anything that the client says and for any issue, debug the user before doing anything else.