If I think of my play of Remake as one full effect...
I think playing Remake pretty clearly involves four effects:
1 Trash a card from your hand (remember its cost)
2 Gain a card costing exactly one more than the trashed card (doesn't matter if that card is not in the trash any more, Remake still 'remembers' how much it cost, it doesn't check the card's cost while it's in the trash or anything like that)
3 Trash a card from your hand
4 Gain card costing exactly one more than the trashed card
Remake doesn't look at your whole hand and try to track each of those cards individually; it just trashes a card from your hand, no questions asked about how it got there or why it wasn't there the first time you trashed a card.
After effects 1 and 3, Remake doesn't try to move a card anywhere, so the lose-track rule doesn't apply to Remake. Even if a card said "When you trash this, put it on top of your deck," Remake would still (try to) gain you a more expensive card, even though the trashed card didn't stay in the trash
Let me try using Donald's scheme from this post
I play Remake. As a default, Fortress' "findable field" would be marked as 1. Fortress is moved to the trash. It's findable field is still 1; Remake knows where it is. Fortress now moves itself back into my hand. Relative to remake, Goko should now set the "findable field" to 0, since something else has interrupt the resolution of Remake and moved Fortress. Remake now continues resolving, but if I choose to trash Fortress again (and I totally agree with everyone that Fortress is in my hand again when I make this choice; I never doubted that), it's findable field is 0. I could at least see this leading to a bug.
I think it would make sense for Fortress's findable field to be set to 1 when it's trash effect happens. I can't think of anything that this would break. If there was a Thief-for-Actions (ie worded exactly like Thief, replacing "Treasure" with "Action"), that would try to gain Fortress out of the trash and fail, so that would matter, but no card like that exists, so it doesn't matter.