I was thinking - 2023 Nebula gets part of her arm burned off getting the stone from the vault in 2014.
Rhodes was there and saw that.
He poofs back to 2023, she gets stuck behind and captured by 2014 Thanos.
2014 Nebula takes the gold plate off 2023 Nebula to pretend to be her.
She poofs back to 2023 and the way things were set up she returns the same time as everyone else.
Rhodes does not notice that her arm that was burned off was is just fine all of a sudden?
And also come to think of it - isn't the 2023 Nebula arm more metallic anyway, and 2014 Nebula's is not, and not one person noticed that either?