Let's assume I run putty on windows and connect to Debian Jessie remotely. I run Midnight commander, and run long term task. Than got power loss on Windows, so putty connection is lost.
Of course I should use screen, but i forgot.
After reconnection I can see mc in ps ax.
1864 pts/3 S+ 0:10 mc
Is there a way to reconnect to this process? (And is it running?)
Nope there isn't, that terminal from where you have launched Midnight commander was the parent process. Once the parent dies the child will die. You should have used screen or disowned the process some how, but now its gone.