There’s an AppKit method that does exactly what (I think) you’re asking for: -[NSWorkspace showSearchResultsForQueryString:]
, which means you can use it using AppleScriptObjC. So, in AppleScript Editor, File > New from Template > Cocoa-AppleScript Applet, then:
property NSWorkspace : class "NSWorkspace"
NSWorkspace's sharedWorkspace()'s showSearchResultsForQueryString_(theFind)
Alternatively, you could skip AppleScriptObjC and use the hidden Finder command that that method uses:
tell application "Finder" to «event aevtspot» theFind