With 'departure' (as in re-materialization) out of the question, 'apostasia' becomes more interesting if we consider that it sometimes has to do with real estate and/or divorce (BDF Lexicon). Look at them from both directions. There is no clear indication from the passage as to who is doing the forsaking:
Real estate:
This would mean the rebellious party is considered to have abandoned the 'property' which God wanted them to have. The unbelieving Jews of that generation did not take up the mission God wanted them to do.
Or, if God is doing the abandoning, God abandoned them and abandoned that property.
Divorce:
Is Israel being abandoned for not taking up the mission of the Gospel? Or is Israel the one who is abandoning the marriage?
All that just to point out the obvious that the Scripture makes obvious - that 2 Thess. 2:2 is referring to "a falling away" or "the departure" from Moses.
2 Thessalonians 2:10 And with all deceivableness of unrighteousness in them that perish; because they received not the love of the truth, that they might be saved. 2:11 And for this cause God shall send them strong delusion, that they should believe a lie: 2:12 That they all might be damned who believed not the truth, but had pleasure in unrighteousness.
2 Thessalonians 2:8 And then shall that Wicked be revealed, whom the Lord shall consume with the spirit of his mouth, and shall destroy with the brightness of his coming:
1 Thessalonians 5:3 For when they shall say, Peace and safety; then sudden destruction cometh upon them, as travail upon a woman with child; and they shall not escape.
Daniel 11:21 And in his estate shall stand up a vile person, to whom they shall not give the honour of the kingdom: but he shall come in peaceably, and obtain the kingdom by flatteries. 11:22 And with the arms of a flood shall they be overflown from before him, and shall be broken; yea, also the prince of the covenant. 11:23 And after the league made with him he shall work deceitfully: for he shall come up, and shall become strong with a small people. 11:24 He shall enter peaceably even upon the fattest places of the province; and he shall do that which his fathers have not done, nor his fathers' fathers; he shall scatter among them the prey, and spoil, and riches: yea, and he shall forecast his devices against the strong holds, even for a time.
Daniel 11:32 And such as do wickedly against the covenant shall he corrupt by flatteries: but the people that do know their God shall be strong, and do exploits. 11:33 And they that understand among the people shall instruct many: yet they shall fall by the sword, and by flame, by captivity, and by spoil, many days. 11:34 Now when they shall fall, they shall be holpen with a little help: but many shall cleave to them with flatteries. 11:35 And some of them of understanding shall fall, to try them, and to purge, and to make them white, even to the time of the end: because it is yet for a time appointed. 11:36 And the king shall do according to his will; and he shall exalt himself, and magnify himself above every god, and shall speak marvellous things against the God of gods, and shall prosper till the indignation be accomplished: for that that is determined shall be done. 11:37 Neither shall he regard the God of his fathers, nor the desire of women, nor regard any god: for he shall magnify himself above all. 11:38 But in his estate shall he honour the God of forces: and a god whom his fathers knew not shall he honour with gold, and silver, and with precious stones, and pleasant things.
Daniel 2:34 Thou sawest till that a stone was cut out without hands, which smote the image upon his feet that were of iron and clay, and brake them to pieces. 2:35 Then was the iron, the clay, the brass, the silver, and the gold, broken to pieces together, and became like the chaff of the summer threshingfloors; and the wind carried them away, that no place was found for them: and the stone that smote the image became a great mountain, and filled the whole earth.
Daniel 2:44 And in the days of these kings shall the God of heaven set up a kingdom, which shall never be destroyed: and the kingdom shall not be left to other people, but it shall break in pieces and consume all these kingdoms, and it shall stand for ever.
Daniel 2:45 Forasmuch as thou sawest that the stone was cut out of the mountain without hands, and that it brake in pieces the iron, the brass, the clay, the silver, and the gold; the great God hath made known to the king what shall come to pass hereafter: and the dream is certain, and the interpretation thereof sure.
2 Thessalonians 2:5 Remember ye not, that, when I was yet with you, I told you these things? 2:6 And now ye know what withholdeth that he might be revealed in his time.
