Most software these days is configurable, and so comes with default settings. Occasionally even the best crafted software has one or more defaults that just leave me shaking my head.
I'm in the process of upgrading my laptop from Linux Mint Helena to Mint Isadora, having previously upgraded my office machine. I held off on the laptop for a while, partly because I was using hit heavily and partly because I wanted to make sure the office PC didn't suddenly turn into a doorstop, but I decided that today was the day to upgrade the laptop. So I did (well, I'm technically I'm still doing it) ... and suddenly minimized windows started disappearing. Normally they turn into buttons in the task bar (much like Windows, pardon my language), but post-upgrade they just vanished. Googling around, I discovered I was not the first person to notice this, and one of the answers I found involved deleting all hidden files in my home partition (left over from Helena) and rebooting. I was a bit disinclined to try that, partly because I did the office and laptop upgrades the same way (overwrote the system partition but kept my home partition intact), and the office PC didn't seem to have the same problem. But I was on the verge of doing the dirty deed when I found a posted response that solved the problem easily.
The Mint (and Ubuntu) task bar (more properly known as the panel, or Gnome panel, assuming that you are using the Gnome desktop) is configurable. You can right click in an open area in it, click Add to Panel ..., and select various applets to display there. Two of them are Window List and Window Selector. The former is what displays a button for each window. (The latter displays a button that, when clicked, gives a list of windows, from which you can select the one you want to restore.) The dopey thing (to me) is that neither of these is enabled by default.
Now Mint (and Ubuntu) also have a window selection method similar to "Cool Switch" (alt-tab) in Windows, and in fact the default key combo is alt-tab. So if (a) you realize Mint has this and (b) you know the key combination, you can cycle through those invisible (but still open) windows. In fact, if you go to the CompizConfig Settings Manager in the Control Center, you can find some even slicker ways to cycle through windows. (I'm playing with the ring arrangement right now.) Who knows, if I get sufficiently accustomed to tabbing through windows, maybe I'll drop the Window List from the panel -- although I doubt it, as I like to have a visual reminder of which programs are running. But I just can't get past the idea of a default configuration that makes running programs disappear from sight.