HPCV doesnt imply that its been attached to any train or not & may awaiting to b refilled!!
Further, if HPCV has gone, then it will return too, same as like empty freight train!!
PS: Mostly HPCV is attached in trains, which do have total coach count with 13-17 Coaches, excluding HPCV & they never create any cut-off for passenger service!! Exceptionally 24 coacher has been seen attached with one HPCV, making the rake length as 25!!