Suppose there are two branches, master and conflict, they both started from a common branch (or commit) and edited the same file in the same place, therefor resulting in a conflict if trying a Merge or a Rebase operation between the two.

Branch master has the commits & the fictional commit IDs as follows:
Edited file.txt from master - ID 02
Added file.txt - ID 01

Branch conflict has the commits & IDs:
Edited file.txt from conflict - ID 03
Added file.txt - ID 01

Now let's create a detached Head pointing to commit ID 02.

Next, calling the the Rebase action with the conflict branch (open Rebase dialog and select conflict branch), the rebase will fail and the detached Head will point to commit ID 03.

Calling again to the Rebase action, Continue/Abort/Cancel options are given. If the user selects Abort, the rebase operation is aborted, however the detached Head still points to commit ID 03.

Doing the same operations via the git cmd line, after the rebase abort operation the detached Head points to the initial commit, ID 02, and not ID 03 as changed when rebasing.