It was migrated!
Wow, similar situation, the application previously used a small executable on the client site. It was migrated by the vendor to an IIS(eww) server with a banal webpage. The trainer came, the users were trained. It was out of our hands. Sometime later(months?) the server was decommissioned, but not wiped!* A few days later the roars from the finance department were heard all over the office**... We, as in, me and my manager marched in, pulled up the webpage for the new banal IIS webpage, and some strange looks were exchanged between the finance department plebs(I'm sure coins were dropping). During the following days, it was discovered that during the training the cut over date wasn't really defined. So the users kept using the old system. In the end, the vendor was able to extract the months? of work from the old system, and massage it into the new system.
* One colleague wanted it for a test bed, but was too busy to pull the trigger!
**I'm pretty sure that was the day my hair started turning grey.
I feel older just talking about it!