Give this a try (adding dummy rows with 0 count for all msgId_short that you may get, then taking the max count. Anything missing in main search result will show 0 count)
index=app sourcetype=ELP99 host="CHeapp*" source="C:\\TPFiles\\LogFile*.log" sourcetype="etp99"
msgId=LS-* OR msgId=LAS-* OR msgId=LSP-* OR msgId=LRS-*
| rex field=msgId "(?<msgId_short>.*)-"
| stats dc(serverName) as ServerInRotation by msgId_short
| append [| gentimes start=-1 | eva msgId_short="LAS LSP LRS" | table msgId_short | makemv msgId_short | mvexpand msgId_short | eval ServerInRotation=0 ]
| stats max(ServerInRotation) as ServerInRotation by msgId_short
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