The workbook part (Part /xl/workbook.xml [org.docx4j.openpackaging.parts.SpreadsheetML.WorkbookPart] containing JaxbElement:org.xlsx4j.sml.Workbook) lists the worksheets:
Using xml Syntax Highlighting
<workbook xmlns="http://schemas.openxmlformats.org/spreadsheetml/2006/main" xmlns:r="http://schemas.openxmlformats.org/officeDocument/2006/relationships">
<fileVersion appName="xl" lastEdited="5" lowestEdited="4" rupBuild="9302"/>
<workbookPr filterPrivacy="1" defaultThemeVersion="124226"/>
<bookViews>
<workbookView xWindow="240" yWindow="105" windowWidth="14805" windowHeight="8010" activeTab="1"/>
</bookViews>
<sheets>
<sheet name="My Sheet1" sheetId="1" r:id="rId1"/>
<sheet name="My Sheet2" sheetId="2" r:id="rId2"/>
<sheet name="Sheet3" sheetId="3" r:id="rId3"/>
</sheets>
<calcPr calcId="122211"/>
</workbook>
Parsed in 0.002 seconds, using
GeSHi 1.0.8.4
You'll need to remove the relevant sheet from the list of sheets.
The worksheet part will still exist within the package (its a rel of the workbook part). You don't need to remove the part in order to "hide" the sheet in Excel, but you may want to do so if it contains sensitive info or is large etc