Unless the tesseract can get you out of the mystical house of mirrors, they've got themselves a real plot hole here...
And for added fun...
If you have a device that turns back time on any given object, WHY WOULD YOU NOT DO THIS?!
Or this, for that matter. Especially this:
Post-release note: Alas, my clever plot hole is not a plot hole at all. From the Marvel Cinematic Universe Wiki:
Using the Space stone, Thanos can conjure powerful compression forces to create black holes, as he compressed the fragments of the gateway to the Mirror Dimension sent at him by Strange into a small but devastating vortex that gathered up everything its path and sent it flying towards Doctor Strange
This is Thorin, one of my ferrets. Here he is sitting on my cartooning desk like he owns the place. Am I not the king?!