If you play your Estate Map, you can trash a TMap from your hand, but you still won't find anything because you did not trash two TMaps.
Does "another copy of treasure map" refers back "trash this" to be also a treasure map?
I just wanted to ask the same question. It is clear, that you won't gain Golds with this move, but I'm not sure, if you really should be allowed to trash the Estate Map.
Fo me it looks so, that "this" actually refers to "another copy of Treasure Map". Sometimes, if you have to trash or may trash the played card, it tells you to trash "this card" (e.g. Mining Village). As it is here only "this" without "card", I think, that it is meant as "(this and another) copy of Treasure Map", so "this" has to be a Treasure Map too.
(Sure, Urchin and Hermit also only say "this", but there is no confusion with the meaning of it.)So, my solution would be, that you play Estate Map and do, what it says, if possible:
1) Trash this copy of Treasure Map. --> Not possible
2) Trash another copy of Treasure Map from your hand. --> I'm not sure. You can trash a Treasure Map from your hand, but it isn't really "another".
3) If you do trash two Treasure Maps, gain 4 Gold cards, putting them on top of your deck. --> You didn't, so you don't get Gold.