Yes - with each save or campaign adv, all ships marked "Unique" are checked by the campaign and if dead, they are dead:-
This is the roster cfg where unique ships are stated
[UnitClass]
ClassName=BBRoyalSovereign
UnitType=11
AppearanceDate=19160316
DisappearanceDate=19480301
DisplayName=BR BB Royal Sovereign (proxy)
IsUnique=yes
[Texture 1]
TextureName=
LightmapTextureName=data/Sea/NBB_QueenElizabeth/NBB_QE_O01.tga
NormalmapTextureName=
StartDate=19390101
EndDate=19461231
Frequency=1
[Unit 1]
Name=HMS Revenge
DOC=19160316
DOD=19480901
[Unit 2]
Name=
HMS Royal Oak
DOC=19160616
DOD=19391014
[Unit 3]
Name=HMS Royal Sovereign
DOC=19160616
DOD=19490401
[Unit 4]
Name=HMS Resolution
DOC=19161216
DOD=19480501
[Unit 5]
Name=HMS Ramillies
DOC=19170916
DOD=19480301
;************* THE END ***************
And here is the campaign profile for that ship:-
[CampaignProgress.MisResult 15.MisKill 6]
Name=
HMS Royal Oak
ClassName=BBRoyalSovereign
Type=11
Side=1
KillDate=19390930
Tonnage=31000
Long=-356980.218750
Lat=7070345.000000
Height=-12.800246
IsFromSingleMis=false
[CampaignProgress.UniqueShipsStatus 16]
Name=
HMS Royal Oak
ClassName=BBRoyalSovereign
Active=false
Dead=true
As you can see - I sank this ship 30/09/39 and the campaign knows it and will not use it again
Many people here state facts about the campaign engine for SH5, but they have not taken the time to look and thus get it wrong.