That's where your wrong, the state still existed in London and underground
There were few years when Stalin recognized Polish gov. in London (since agreement on 30.07.1941, after Germans invade USSR), of course he did that until USSR take upper hand on east front. Agreement was one-sided broken by USSR on 25.04.1943.
Anyway that short period of cooperation had some highlights, actions against Poles in USSR were stoped to some extent, and Stalin agreed to let go some of Poles (including those who were kept in Gulags and prisons), and let them to create Anders Army. According to different sources thanks to that agreement about 41000 of soldiers and 74000 of civilians were let go from Gulags (Poles, Ukrainians, Belarusians and Jews). Those people flew from USSR via Iran, part of them stayed in Anders Army. Those soldiers fought against Germans in Africa and later in Italy, for example in battle on Monte Cassino. Anyway, after Stalin broke agreement, he started to create his own Polish army under communist leadership.
Did Poland lost the war? Yes, one of the two invaders won. But Poles had to cooperate with one of them to survive. I've read somewhere, that added up Polish forces were fourth largest army in WWII in Europe, bigger than France forces. But due to disperse (east front, west front, Africa, Middle East) political power of Polish authorities was small. At least Poland didn't become one of the USSR republics.