This depends on when the hand and the bat became separated. If the bat became separated before the batsman made their ground, then the batsman is out as they never made their ground. If the batsman made their ground with their bat but then dropped the bat, they are considered to still be in their ground; quoting Law 30.2:
However, a batsman shall not be considered to be out of his/her ground if, in running or diving towards his/her ground and beyond, and having grounded some part of his/her person or bat beyond the popping crease, there is subsequent loss of contact
[...]
between the bat and person, provided that the batsman has continued movement in the same direction.
