They were in a regular window, but they are not in History, since I have not activated them recently (on browser start tabs are loaded as inactive/frozen and have to be activated to be loaded and stored in history).
I'm afraid information about all those closed tabs has been wiped out of Opera Mobile memory in the moment of closing them... 😞
BTW, only about 10 tabs are on the list of Last closed tabs, so looks like the others are lost for good...