Either this is a Windows limitation or there's a minimize bug when using the Secure Overwrite feature that uses another window within the main program GUI to display the on-going status.
How to reproduce (I've did this twice):
1. Minimize Recuva during a Secure Overwrite. I let it completely finish with the overwrite. Finished will be indicated when the minimized window for it in the systray blinks a few times.
2. Now Recuva can't be brought back into view by clicking it in the systray, it's completely stuck there, there's also no right click options for it either. It also can't be switched to using ALT+TAB. The only way to exit Recuva at that point is to End Task it using Task Manager.
Info:
* Recuva v1.52.1086 (most current version)
* WinXP Pro SP3
Hey, I have this problem too, it's really annoying
I’m on Windows 10 64bit and I cant get it back on the screen using alt+tab, maximize or even using the multi desktop function
Though I can see the window using windows Aero and i was able to take a screen capture while aero was showing the window preview: 
This really annoys me as I don't know if the drive wipe is complete or not
Also, recuva is only on this window, there i no loading window of any kind at the moment i took this screen cap
When I click on the previewed window, it instantly disappears from the screen
Also I have 3 screens on this PC if that’s the cause, I also have these CCleaner monitoring on as well as these programs running:
Chrome, Steam, Skype, AMD Radeon settings, Logitech Gaming Assistant, Razer Synapse, MSI fast boot, Google Drive, Realtek HD audio, Epson printer service and Veracrypt
Hope this info will help devs to fix that issue
Minimize bug still exists in Recuva v1.53.1087.